After a while the css breaks

Hello,

I’m using Autoptimize for about 1 year now and I’m really happy with it.
Only I’ve got this one problem where the CSS can be found but doesn’t work at all. (just like its not found)

I have to clear the cache to fix the problem.
The weird part is that it’s completely random, some times it happens after 2 weeks and other times just after 1 day.
Cache amount is never hight always max 20mb.

Plugins I use that are worth mentioning:
– Autoptimize
– ACF
– Cache enabler (by keycdn)
– Yoast SEO
(and many others but I don’t see them breaking anything)

The css is included in the functions.php (the wp way)

What am I doing wrong?