I’ve been using Audacity for years, both Win7 and Win10. I recently upgrading both of my computers (one older Win7 and one brand new Win10) to 3.0.3 and now BOTH have this issue: when editing, I cut some room tone from the end of my recording, then I use it to paste over breaths and various other points in my recording. I can roll this way for a while… maybe a couple of hours or so… and then it will start getting slower to respond… then the spinning blue circle… then NOT RESPONDING. After that, I’m done. Every edit, even after a restart, takes minutes, and eventually NOT RESPONDING. The only solution I’ve found so far is to completely UNINSTALL Audacity and REINSTALL. After that, I’ll get a couple of hours of good fast cuts and pastes without any delay… and then the first delay, and then NOT RESPONDING. Then I start all over again.
I repeat that I did not have this problem with the older versions of Audacity (and I don’t know what that version was, but it was a few years old, so 2.something?).