Banging Norcold

[Russ in California]

I have an older Norcold that seems to work fine. Got it down to -1.5 degrees. It's older so I worry that it draws more like an old house refrig. When this puppy is mounted up in the LC, strapped down, it will bang on some bumps. We're just talking around town and such. It sounds like it's the inside of the compressor or ?swing motor. It doesn't sound too good sometimes and that can't be good for it. It appears it's mounted well in the chassis. Doen't seem to move much at all. There's some little rubber mounts that are in good shape. It just bangs like a steel ball in a metal tube.
Any ideas if this is a bad thing?
In anticipation of ?... I bought a second cooling unit/compressor off ebay. Hooking it up is a another thing now. Ouch. Thought I'd just swap it out and have a NOS cooling unit. We'll see.