edited

it sounds like it needs to be cleaned better, it's the Castor Oil that has hardened, you could wash it out very-very good with hot-hot water (the heat will melt the Castor), then rise with rubbing alcohol to get the water out, then once dry re oil, or better yet soak in Antifreeze in a crock pot for 5 or 6 hours, the Antifreeze will clean it, then rinse well with rubbing alcohol, dry well and re oil,,, then see if it turns over smoother

Jim