If it is the O ring, why was it difficult to replace? I think it takes 5 minutes! Pop the start cap off, unscrew the two mounting screws. Use a pen to mark the polarity on the PCB and starter mount. Pull out the starter assembly. Two cuts with a sharp scalpel and dig out the O ring. Clean the mounting cavity with a Q-tip and CA kicker. Squeeze in new O ring, replace the starter, screws, cap and it’s done.
If the turbine is free and the O ring is not slipping it can be the motor brushes are dirty/warn.