Windows 11 takes more than 1 hour to shutdown if running Dropbox desktop app

Hello,

I have the "Plus" version of Dropbox, with the desktop app installed on a Win11 machine.  All drivers and updates completely up to date.

When running Dropbox, and trying to shutdown, the Win11 machine takes over an hour to shutdown.

!!!

If Dropbox is not running, the same machine shuts down in about 1 minute.

The issue seems to be unique to this machine, my other machine with Dropbox installed seems to work "normally", and shuts down in a normal amount of time also.

Windows File Explorer indexing is disabled (per suggestions found online).  Having indexing on or off hasn't made any difference.

My current Dropbox usage is (after paring this down a little):
1.77 tb (with a limit of 2 tb), 
348K files across 35K folders.  
I'm a commercial photographer, and most of the Dropbox storage is for my active Lightroom catalog. 

The catalog itself is
1.45 tb
65K files

One other indicator that all is not right:  syncing files on this machine seems to be hung.  It's been trying to sync about 40 files for 2 days, something that should take a couple of minutes.

Network speed:
600 mbps down, 20mbps up.

Dropbox files are stored on an external USB 4tb drive (about 50% full).  Performance on this drive is slow, but not sure why.  

Not sure if the drive is the cause of the issue, or if it's a victim of something else that's going on.

Looking for help please...

Thank you!