had the same issues with my trs's
all previous recs are good points. Also found that once new motors or rebuilds had been completed, check all elec leads and make sure the terminals are well connected. also check for leaks i had one oil line weaping causing one drive to dip slowly over time.

Like Biggus mentioned if you pull the rams off at the back of the drive and see if you can rotate the end freely. If you can't you have to rebuild the ram. It is fairly easy to do and not super expensive.

Thanks for the great info!..I have the exact same boat with the exact same issue. Now I know what to do with it.

Do you need any special tools to be able to rebuild the trs rams? I've done small equipment cylinders before and they weren't bad. Any recommendation for locating a rebuild kit for them? Thanks.