Vortex Diatom Filter Problems

I have a Vortex XL that has been giving me some trouble in the last few
months. I've had the filter almost a year and kept up with maintenance
and have been impressed by how well it works until now.

The motor keeps seizing up on me. I've taking it apart and thoroughly
cleaned and lubricated it several times. Yesterday it would only run a
few minutes before making an awful screeching sound. The problem is
right where the top most portion of the shaft seats in the motor. It is
very difficult to impossible to get that just right. I used an all
purpose grease the last time and had the best results with that and by
best results I mean the longest period without it seizing up.

Anyone else have similar problems and how did you resolve?

Thanks