You know of course that NONE of this makes any sense with the info you have given us so far? I could maybe see a bad internal drive causing this issue, BUT, the EXACT same issue of corrupted recordings that nobody else has seen happen in this way, and only YOU have the problem on 3 receivers?
There HAS to be some other commonality. That means we need more information. How is your whole system laid out, Eastern arc, Western arc, what dish(es), what channels are the recordings from, are they OTA, are they ALL satellite, etc, etc. SOMETHING in that whole mess has to be causing this issue. Realize that your entire satellite system install is the only common part of this whole ordeal.
So, I'm saying it's NOT the receivers, but some other strange phenomena with your system or connections that is causing the corrupted recordings. I'll bet money they are corrupted when recorded, but you don't notice the issue until the external drive move attempts to do whatever exact functions it does when commanded.