Delete existing Time Machine backup and start fresh

I'm at v. 6.10.2

X-RAID/RAID-5

Time Machine backup from Mojave over SMB

I just expanded storage by replacing 2 drives. Original configuration was 4x1TB drives. I replaced the first two of these drives, one at a time, allowing a complete resync between each, with 2TB drives. Volume resync'd after each new drive, and all's well.

Now, however, my Time Machine backup doesn't work. It lingers over "Preparing Backup", then times out and quits. I've got two other backup strategies going, so I'd be okay with completely deleting the current TM backup, re-allocating, and starting fresh.

Oddly, Time Machine "Verify Backup" checks out.

I have been unable to find documentation on how best to do this, and would appreciate any guidance.

Thanks!