Do these systems perhaps have Decklink cards installed for output?
I have seen a LOT of crap with latest Decklink drivers.
Including Out of Memory.
Check if the problem persists with External video set to OFF.
What kind of footage/sequence settings?
Also don’t set your UNDO levels to high.
FCP can only adress 3GB ram.
Also check your Still Cache. Shouldn’t be higher than 10/30%