Issues with png -> webp conversion

Hey folks,
in the current FluentCommunity version I’m having trouble with the conversion from PNG to WebP.
When I upload a PNG image, I always see “loading failed.” But if I upload the same image directly as a WebP file, everything works fine.

I’m using S3 as my media storage, but that shouldn’t be the issue, since it would fail with WebP as well if that were the case…

The strange thing is that it doesn’t fail everywhere.
For example, if I upload a space banner via the admin menu → “loading failed.”
But if I upload the banner directly within the room → it works.

Is anyone else having this issue? Any ideas what could be causing it?
I didn’t have this problem with older versions. And I don’t see any errors in the WordPress debug logs.