First of all thanks for reporting here (the thread dump was really useful) and for your patience.
Here is the situation: if your project is bound to SonarQube/SonarCloud and for any reason the server is not reachable (e.g. network outage, server not responding, on a different VPN), the IDE will eventually freeze.
This problem is caused by a combination of different flaws in our plugin. We have identified some of them (here, here and there). We already have a fix for the 2 first ones, that would help mitigate the issue (at least the UI shouldn’t freeze anymore), and we are thinking about the right solution for the third one which is a bit more involved.
There is unfortunately no workaround that you could use, apart from making sure that the server your project is bound to is reachable while developing. I know, this is not ideal.
We are sorry for the inconvenience and we will keep you informed as soon as we make progress.