Hi!

No cache plugin is active. When switching “Delete Old CSS And JS Files?” option, the cache seems to be deleted, but then again, all posts of the CPT is getting the same CSS class and therefore same rules apply.
The problem is not the external cache, but the avia cache. It is wrongly assigning background-image to element class, although it is different for each post.

It should either add background-image as inline style as in my example or generate a unique uid for each post.

Regards
Bence