Here's a weird one. For 98 out of 100 searches the cart works great and provides search results. the other 2 times (for different search words) it produces blank pages.
Here is the error log.

[21-Jan-2021 12:48:16 America/Chicago] Request URI: /index.php?main_page=create_account, IP address: 176.111.51.85
#1 header() called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/html_header.php:16]
#2 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/html_header.php) called at [/home1/pegasuspub/pegasuspublishing.com/index.php:42]
--> PHP Warning: Cannot modify header information - headers already sent by (output started at /home1/pegasuspub/pegasuspublishing.com/includes/languages/english/extra_definitions/fluorspar/extras.php:1) in /home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/html_header.php on line 16.

[21-Jan-2021 12:48:16 America/Chicago] Request URI: /index.php?main_page=create_account, IP address: 176.111.51.85
#1 zen_categories_ul_generator->buildBranch() called at [/home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php:85]
#2 zen_categories_ul_generator->buildTree() called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_mega_menu.php:35]
#3 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_mega_menu.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php:116]
#4 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php:106]
#5 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php) called at [/home1/pegasuspub/pegasuspublishing.com/index.php:94]
--> PHP Warning: A non-numeric value encountered in /home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php on line 58.

[21-Jan-2021 12:48:16 America/Chicago] Request URI: /index.php?main_page=create_account, IP address: 176.111.51.85
#1 zen_categories_ul_generator->buildBranch() called at [/home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php:85]
#2 zen_categories_ul_generator->buildTree() called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_mega_menu.php:35]
#3 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_mega_menu.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php:116]
#4 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php:106]
#5 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php) called at [/home1/pegasuspub/pegasuspublishing.com/index.php:94]
--> PHP Warning: A non-numeric value encountered in /home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php on line 73.

[21-Jan-2021 12:48:16 America/Chicago] Request URI: /index.php?main_page=create_account, IP address: 176.111.51.85
#1 zen_categories_ul_generator->buildBranch() called at [/home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php:85]
#2 zen_categories_ul_generator->buildTree() called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_mega_menu.php:35]
#3 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_mega_menu.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php:116]
#4 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php:106]
#5 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php) called at [/home1/pegasuspub/pegasuspublishing.com/index.php:94]
--> PHP Warning: A non-numeric value encountered in /home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php on line 73.

[21-Jan-2021 12:48:16 America/Chicago] Request URI: /index.php?main_page=create_account, IP address: 176.111.51.85
#1 zen_categories_ul_generator->buildBranch() called at [/home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php:85]
#2 zen_categories_ul_generator->buildTree() called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/templates/tpl_modules_mobile_categories_tabs.php:32]
#3 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/templates/tpl_modules_mobile_categories_tabs.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php:120]
#4 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php:106]
#5 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php) called at [/home1/pegasuspub/pegasuspublishing.com/index.php:94]
--> PHP Warning: A non-numeric value encountered in /home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php on line 58.

[21-Jan-2021 12:48:16 America/Chicago] Request URI: /index.php?main_page=create_account, IP address: 176.111.51.85
#1 zen_categories_ul_generator->buildBranch() called at [/home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php:85]
#2 zen_categories_ul_generator->buildTree() called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/templates/tpl_modules_mobile_categories_tabs.php:32]
#3 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/templates/tpl_modules_mobile_categories_tabs.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php:120]
#4 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php:106]
#5 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php) called at [/home1/pegasuspub/pegasuspublishing.com/index.php:94]
--> PHP Warning: A non-numeric value encountered in /home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php on line 73.

[21-Jan-2021 12:48:16 America/Chicago] Request URI: /index.php?main_page=create_account, IP address: 176.111.51.85
#1 zen_categories_ul_generator->buildBranch() called at [/home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php:85]
#2 zen_categories_ul_generator->buildTree() called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/templates/tpl_modules_mobile_categories_tabs.php:32]
#3 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/templates/tpl_modules_mobile_categories_tabs.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php:120]
#4 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_header.php) called at [/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php:106]
#5 require(/home1/pegasuspub/pegasuspublishing.com/includes/templates/fluorspar/common/tpl_main_page.php) called at [/home1/pegasuspub/pegasuspublishing.com/index.php:94]
--> PHP Warning: A non-numeric value encountered in /home1/pegasuspub/pegasuspublishing.com/includes/classes/categories_ul_generator.php on line 73.

I really need to get this fixed.