Roamio-to-Roamio transfers permanently delete existing shows on target Roamio!

Forgive me if this has been discussed before. If so please point me to a relevant thread.

I am preparing upgrade a Plus to an 8 TB drive. I wanted to save 10 TCM movies from the original drive so I initiated transfers from the Plus to my Pro (3TB) that was 90% full.

When I checked the target Pro's fullness while the 9th movie was transferring it had plummeted to 71%. The 10th movie caused the fullness to drop to 66%. Therefore, that 10th movie (6 GB) caused the erasure of ~150 GB of older...

Roamio-to-Roamio transfers permanently delete existing shows on target Roamio!

Roamio-to-Roamio transfers permanently delete existing shows on target Roamio!