I also just tried something out of interest. I tried in Chrome/Firefox and Edge for all 3.

I uploaded v1.5.5 admin/user_tracking.php and I get as I mentioned the page loads but then all the table data is reported but commented out.

I uploaded v1.5.4 same file and I get a blank page completely so nothing loads (not the menu, etc.).

I uploaded v1.5.3 same file and it works flawlessly seeing all the data.

I uploaded v1.5.2 same file and it also works flawlessly.