Just updated to 2024.1 and it still happens. And for me it's not how long Max has been open, but rather the scene size. I just opened a large scene, messed with the new slate material editor, and tried to close it after 5 minutes of being open. It's been sitting there for at least 5 waiting to close....
Latest DB of corona, latest forest pack, Windows 10, 3970x w\ 128gb ram.