Customer Details Missing from Address Book Table

Zencart 1.5.6 Php 7.2.

Hello,

I have found the strangest problem today.

A customer tried updating their address and received a database error; standard error with no codes. Nothing in the error logs. When trying to update his address in the admin, everything in the fields go back to blank.

I checked the tables in the database and he is in everyone except " address book" there is line numbers and those have not been skipped, e.g 1, 2, 3 etc. Where his ID number would be, the number isn't there. It skips the number but not the line number e.g 1, 2 etc.

How would i correct this? I'm not sure where his line details went from the database in that particular table. I'm at a loss on this one.

Thank you in advance.