I have a 2-monitor setup on my iMac.
When I create a new Balsamiq project, it appears in my right screen. When I try to drag it over to my left screen, it starts jumping around and disappearing. I don’t experience this with any other apps, and it only started happening with v3. I have the latest version.
After a few goes it lets me do it, but it’s super weird and buggy. I have a video of the issue if that helps?