Hello there, and welcome to the forums!
I’m sorry to hear about your experience. The “black circle overflow” bug has in fact been noted for a while, though it’s had different causes - many of which have been fixed. This is something I myself actually encountered and reported back before joining the team here! That specific case, with my feedback, was able to be identified and fixed, though as mentioned there is still a way to cause it.
We do get infrequent reports about this issue, however we’ve not been able to reproduce it internally, nor have any reports been able to find a way to reliably reproduce the issue (or at least reported a reproduction case) for us to reliably investigate.
All bugs are bugs we want to fix, however we also need to prioritize bugs. With this one in particular, it’s a bug which is rare to happen, and doesn’t currently have a known reproduction. This means to address it, we would need to pull apart any and all related code to try to identify where it could possibly be happening, taking an unknown number of hours (likely a lot with this approach) to correct for the rare cases where it comes up. When prioritized against other bugs, which have known reproduction/causes, effect larger number of players/occur frequently, and/or have a known time to fix, those need to be prioritized first. This is pretty normal in any sort of development work.
This is not in any way to diminish the poor experience caused by this bug, and It’s certainly unfortunate that this means some rare bugs like this can stick around for a while. But if you’re able to identify a way to reproduce the issue, and let us know that would help greatly to get this resolved sooner. It sounds like this was happening to you with some frequency, so it may be possible you could be the key to finding the cause! We’d be very happy to get a reproduction case for this so we can get it fixed.