Lightroom Classic v15.5.1 sync on Mac with Tahoe not working but no errors listed anywhere

Using LrC 15.5.1 with CC subscription long term on a new MacBook Pro M5 running Tahoe 26.6.2.

Sync generally worked with v15.5.1 previously on my M1, but since migrating to the M5 a few weeks ago not so much.

I have about 50,000 photos and am trying to sync them in batches of 2000-4000 at a time. They start syncing fine and then at some point it just stop working and gets hung on a file.

I'll just see the sync Local Activity in top right of LrC say it's syncing the same number of files (ie; remaining files) and hasn't changed in hours.

In Lightroom Sync tab in Preferences, the same photo is listed at the top of the Sync Activity window and it hasn't changed for hours.

The photos all say "Image" in the Sync Activity window of LrC and nothing lists any kind of error.

I tried selecting the very top photo and applying a minor edit to see if that would "kick start" the process (the previous fix for some earlier versions of LrC) but no change.

There no Sync Errors or Sync Error Album anywhere and there is nothing in the Deleted Album folder on Lightroom on the Web.

Any other suggestions on what to do to get Sync Service/Engine working? Am I missing another potential area to troubleshoot?

Thanks.