Finally managed to update osTicket now. It is released as a major version change in the package, which requires manual update. This is because upstream changed the way email is handled and the new package removes the automatic email setup, enabling instances to also use off-Cloudron mailboxes for support ticket handling.
I am not certain what might have happened but I am guessing that I was somehow mistaken about the IMAP/SMTP settings getting reset because they did not break even after a Cloudron update occurred. However, I am starting to suspect that brower autofill is responsible for what I was observing. Thanks for taking a moment to consider my issue.