Thank you @Andreas_Hegenberg. FWIW: The issue subsides immediately after restarting the BST app, but then returns a while later – usually after switching apps and coming back to Vivaldi or InDesign.
Once the workaround has been tested & verified I will push a new BetterSnapTool version to the store as well!
Hello Andreas. I just wanted to check back in and let you know that the issue seems to have subsided recently. I'm not sure if it was something you did, or something that updated in Sonoma, but it seems to be fixed (at least temporarily)!