Mickey2 - May I suggest trying the solution that they used in the Victorian era for these machines that have become "sluggish by dried up oil.
Many of the early machines came with two "oil" cans. one is for oil the other for kerosene. If a machine is stuck or sluggish, perform your typical oiling process but use kerosene. it will break down the old dried oil. then do the process two more times, both with oil. the first oiling flushes out the kerosene, the second oils the machine.
I have used this process on over a dozen machines and it so far has worked every time.