Might be related to:
https://www.concrete5.org/community/forums/customizing_c5/video-in-y...

Unfortunately we have no solution.

I'm having the same issue. With block cache turned on, the css files for some blocks aren't being loaded

Are these custom blocks, marketplace packages, or core blocks?

Hi. One is a custom block that came with a marketplace theme (Fresh). The other is the core testimonial block but I think the theme comes with a stylesheet that overrides the standard formatting (it's not a custom style applied to the block, I think the developer programatically adds it if there's a testimonial block on the page).

In my case the blocks are

marketplace: pure accordion
core: youtube and google maps

You can check the flags inside the block controllers that dictate the circumstances under which they are cached. Sometimes custom blocks are over-optimistic about when they can be cached.

Hard coded blocks may not automatically pull in other assets such as css and js files. Sometimes an asset required in a block view will be loaded when the cache is off, but not loaded when the cache is on. That can make it difficult for a custom template to add template specific assets without also overriding the block controller.

A quick fix that doesn't require any coding is to use a 'header extra content' attribute to add a <link> tag to a page header for the missing css and force it to be loaded.

If you can do a bit of php and the missing asset is used on most site pages, you could also build loading it into the theme header.

(For an accordion, yuu could use Magic Tabs
https://www.concrete5.org/marketplace/addons/magic-tabs1/... )

Thank for the information. As a normal user I'm unable to patch my site. The question remains: why has this changed from v8.3.2, when everything was working fine?

If it is a backward compatibility issue between v8.4 and v8.3.2 and not any other change of circumstance, or just a problem that was not previously noticed or not previously visible, you will need to ask Korvin for a detailed analysis.

Ok then, what or who is Korvin?
Will it be solved in 8.5.

Korvin is the core team developer who orchestrates this. You can contact him via this site PM (look him up on members), by c5 on Github or by the slack channel.

Thanks. I will try to get attention on that subject.

We're still having problems activating block-cache in v. 8.5.2
Some blocks mentioned above are still not working with cache on.

Has anybody found out in the meantime?