Who can tell why it’s eating couplers?
I guess that's an hydraulique pump, so the unbalance can be discarded. Probably not a bent shaft nor a bad bearing.
It would be nice to have a pic of the other parts and some measurements because it's hard to tell what goes where with certainty ( perspective and different pics) and the system looks a bit strange to me.
The pump's mounting looks fine, excepted being trashed in the inside by some of the bolts coming loose. The main suspect for me is that the circular plate is bolted to the engine by two rows of four bolts:
The outside row holds the pump's mount and the circular plate at the same time.
The internal bolts' raw is the problem, beside coming loose: the plate has no support under these bolts against the load created by them. I only guess for the respective diameters, but for me, there's a gap between even the inner peripheral support and the threaded mounts on the casting ( the closest ones to the shaft). I'm not very clear. The plate vibrates under the bolts, so they cant keep their tightening torque and come loose.
What is the purpose of this plate anyway? A dust protector ?
As a solution, if you ask it, I would suggest, either suppress the internal row of bolts (actually I don't find their utility) or reduce the OD of the plate to make it fit in the deepest circular recess. With the second solution, the external bolts' row holds only the pump's mount, the internal row holds alone the circular plate, but with a real tightening.
Maybe...
For which engine is this cylinder head with the giant valves?