Hello, this is a relatively new install. Just set it up about a week ago. I have had this issue since the install and it continues after I updated the app and database to latest today.
I can add licenses, I can add licenses from templates. That works fine. When I edit an existing license for a client, the post.php page results in Error 500. The information from the edit is saved correctly however.
File permissions for post.php and some additional pages for comparison:
-rw-r--r-- 1 www-data www-data 458375 Feb 13 23:14 post.php
-rw-r--r-- 1 www-data www-data 5875 Feb 13 23:14 product_add_modal.php
-rw-r--r-- 1 www-data www-data 6266 Feb 13 23:14 product_edit_modal.php
-rw-r--r-- 1 www-data www-data 5807 Feb 13 23:14 products.php
-rw-r--r-- 1 www-data www-data 36818 Feb 13 23:14 quote.php
Install is on an Ubuntu 22 LTS VM.
Welcome to Ubuntu 22.04.1 LTS (GNU/Linux 5.15.0-58-generic x86_64)