I have a whirlpool GU980SCGQ3 that the lower arm is not spinning. I posted a while ago about this and wound up cleaning it well which helped temp. there was a lot of soap crud at the bottom.

the upper arm spins fine. there does not seem to be anything blocking the holes on the lower arm. I dont dee all that hard water/soap crud like last time. if I take off the lower arm there is some food paricles I see under a screen but I cant remove the bolt to clean it (prob not prob anyway) the lower arm does seem to not swing freely compared to a relatives that has a sim model. ther seems to be friction?