Robinair 15600 not working vanes seem fine

So I’ve had this Robinair pump for about 2 years with about 3-4 hours of use and yesterday when doing an infusion it started to sputter and the electric motor had some difficulty turning the pump. I Shut it off and whipped out my old fridge compressor and continued with that. Once I was done I took the robinair apart to see if I could find out what’s wrong with it. I thought at first the electric motor was broken but once I disengaged it from the pump part of the system it ran fine. Then I broke down the pump part it self and there’s seems to be nothing wrong with either pump or the vanes. I did note that in the smaller pump the vanes had the beveled edge outward and the bigger pump had the vanes with the beveled side inwards. It seems that the pump will turn freely until I tighten down the plates then it’s locked and won’t turn. Anybody have any ideas as to what could be wrong? It’s crazy to think that my old fridge pump is more reliable than this $300 pump.

Any ideas?

I have two of the same pumps, the only time that I had an issue with one of them was when running it continually with a tiny leak in the bag, it seemed to want to seize.

I now make sure that my bags do not leak, I still run it continuously but have not suffered that issue again since. I did also give both my machines a service and changed the oil.