If you put oil in the oil holes that are in the crank handle opening as advised by Happijac, some of it end up inside just as pouring it down the gears with the electric motor removed.
Extra oil shouldn't cause an issue like this. The old Johnson and Evinrude electric transmission used this type of design but submerged it in oil and it worked great.
I could see where something under the spring could be a problem or the shaft surface under the friction spring could get worn or the spring get broken could possibly be a factor.
Speculation...................
