Yes, the files were sent back to the original machine, and are experiencing the same issues.
Tried trashing FCP preferences, clearing the render manager, repairing permissions, and verifying all discs the footage is on (external and computer internals).
This of course means too that I’ve restarted both machines, and relaunched FCP several times.
Also tried opening the footage in Soundtrack and attempted to “resample” at 48kHz even though it already read as such.