GE GSM1800J lower wash arm a stubborn case

[Desert Ratz]

My faithful dishy-washy suddenly got the mid-life crisis. It's manifested by a stubborn refusal of the lower wash arm to rotate. I've ruled out pump and impeller issues, the upper wash arm goes round and round like the wheels on the bus. When I pop the door open for a quick peek, I get squirted in the eye by water jetting out of the lower arm. It just won't spin around. I took the arm off, cleaned up a little crud off the bottom, then put it back in. I can turn it by hand, but with some resistance. How can I go from here?

[AccApp]

It should spin with very little resistance. Was it jammed before you took it apart? 

[Chat_in_FL]

Spray Arm – Check to be sure the spray arms spin freely and jets are not clogged. Also check that the spray arm is not split, and that you have the proper water level after fill.

[Desert Ratz]

Water level is well above the heating element. Spray arm doesn't appear to be cracked. Spray arm not clogged. Spray arm did turn with basically the same amount of resistance before I took it off to inspect the space between the arm and the thingamajigus that it rides on. So no, it doesn't spin freely. Guess that's my question -- how do I deal with that?  Thanks. 

[Kendell]

take the arm back off   You will find that something is not assembled correctly. The arm should spin freely

[Desert Ratz]

Well, taking it apart, putting it back together, resolves issues. Sounds like typical "operator error."  Thanks all!