LRC Back-up running a lot slower

My Windows 10 LRC catalog has 183,500 images imported over a 13-year period, starting in LR3.

Since v12, when I initiate my LRC shutdown, my 12Tb WD Red (50% empty) hard drive spins for six and a half minutes before LR's Back-up dialog appears.

After I click on Back-up, the PC stays on "backing up..." for about nine minutes, and the green progress bar stays about 2mm wide.

Then, it takes about one minute to copy the catalog, about one-and-a-quarter minutes to optimize the catalog, and one-and-a-quarter minutes to compress the catalog, then shutdown completes.

I back-up once a day and regularly delete back-ups that were more than two weeks old.

LRC back-up never advises there are any database integrity or optimization issues.

Error-checking the drive in Win10 reveals no issues and it is 0% fragmented.

Can I get "back to normal" back-ups by:

- creating a new LRC catalog; if I did, would I lose all my cataloged edits?

- uninstalling/reinstalling LRC and connecting to my existing LRC catalog?

Is there a utility - other than Verify Integrity/Optimize Back-up - that could examine my back-up .lrcat, expuging any file corruption, etc.?