Filter Plugin - modal dialog receives windowWillClose after 20 seconds (Big Sur)

Hello,

Since updating to macOS Big Sur my Photoshop plugin behaves weird... The modal dialog wit hte plugin UI receives windowWillClose after exactly 20 seconds after launching the plugin from the filter menu.

Everything gets released and the plugin is unusable - I need to close the plugin window manually. 
The plugin used to work properly and the only thing that changed is the macOS version.

This looks like some kind of mechanism - the main window of photoshop is "blocked" but the modal plugin window and the parent window tries to close it after a given timeout. It's always 20 seconds.