Here is a useful reminder from a few years back – “SugarCRM cache directory – it is NOT a cache directory!“. Unlike most modern day web applications, which use cache/ folder for temporary files, which are safe to delete, SugarCRM keeps a bunch of stuff in there, which, if disappeared, would leave you in a very uncomfortable and confused stay.
Things have obviously improved over the years, but it’s still far from perfect. And while we are on the subject of surprising issues with SugarCRM, make sure check my other post about working with encrypted values. Basically, the summary is: backup, backup, backup! If you want to sleep well at night, backup SugarCRM’s full file system (files, configurations, temporary files, caches, etc) and its database. And never ever change anything.