I keep getting these warnings. Is this already known?
Yes, JetBrains are extensively reworking the concurrency model of the platform, and older code in Cursive can cause these problems. The problem is that if you click "Report problem" I think it goes to JetBrains, not to me. It's also annoying to get the details out of the report in any way that isn't just sending it. I'll see if I can reproduce one of these, and see if I can check where the report goes and if I can control that. In the meantime, if you could send the thread dump that would be helpful.
send it here, or via the 'report problem' thingy?
Due to https://github.com/cursive-ide/cursive/issues/3055 reporting currently only works on the EAP, so if you're on stable then here is best. I just reproduced a freeze and the reports do come to me, which is great, but there's a size limit which I'm just deploying a fix for. If you're on the Cursive EAP reporting via the button would be best once I get that deployed (hopefully in a couple of minutes)
BTW hopefully you should have some auto-generated thread dumps from the freezes: https://intellij-support.jetbrains.com/hc/en-us/articles/206544899-How-to-get-a-thread-dump-when-IDE-hangs-and-doesn-t-respond. They might be easier to send.
Ok, you should now be able to report these through the IDE if you're on the Cursive EAP. I'll hopefully get a stable build of this out soon too.