App freezes when loading any project; trashing prefs fixes it temporarily

My app hangs whenever I load a project. Trashing my Premiere preferences solves it temporarily, until I close and re-open Premiere.

I've been experiencing this behavior for the last month or so. I have auto-updates enabled, so I'm always using the current version (15.4.1 build 6 on Mac OS 11.4 at this exact moment).

Here's the flow:

• Premiere Pro opens without problems.
• When I open a project (whether from the home screen or from the finder), the project loads and appears, but a progress bar appears for loading media assets and the app hangs there indefinitely, with the loading bar animation active.
• I found that if I trash prefs on launching the app (option-click to open Premiere), all projects load without problems.
• Premiere functions normally until I quit it. Upon reopening, the bug happens again unless I nuke preferences.
• Trashing preferences in the Finder or on launching the app yields the same positive result.
• This persists across project files, source hard drives, media cache locations, etc.... 
• I have uninstalled and reinstalled Premiere through the Creative Cloud app. The problem was not fixed (except for the very first time launching the app after the fresh install, presumably because the prefs were brand new).

It appears that something is corrupting the preferences file whenever the app closes, perhaps.

I'm getting very quick at syncing my keyboard shortcuts and preferences from Creative Cloud, for minimal downtime, but it's still a pain to deal with. I hoped that last week's update would address this, but nothing changed. I also wonder if the creative cloud preferences/keyboard shortcuts sync is in fact the aspect that is introducing the bug.

I'm very interested to hear if anyone has experienced anything like this before, and if you were able to find a solution.