Well first off out of level is relative.
Here are the specs for my 2003 Norcold model N611 refrigerator.
Refrigerator specs legal operation 3 degrees front to back (of trailer), 6 degrees side to side.
Note 3 degrees would be 12” difference front to back on my 21’ trailer! Note 6 degrees would be 8.6” difference side to side at the tires!
Note older fridges needed to be more level than this.
When trailer is moving, no problem. When sitting I was told that it starts to degrade almost immediately, so I should turn fridge OFF if left unlevel per above, even if I was just stopping for lunch. They said degradation was progressive, so each time I did it fridge was damaged just a little more. True? Your guess, I just did it anyawy to be safe.
Note rarely parked that unlevel anyway.