Update (in case anyone is still around for this): this still happens on the latest version, but NOT when the condition is, for example, “post type is equal to post”, but it does when the condition is category or taxonomy. I hope someone has a fix for this.
So I have this problem, yet oddly enough only on one single website. I use the same host for all my sites. No errors show up. If there would be a workaround this would be great, assuming the problem is indeed known.
Edit: I did update to 6.0.1 and the problem persists, so the mayor update didn’t solve it for me.
