Try a tad leaner - in increments of under an 1/8, just nudge under the width of your screw diver. I can´t believe that the bearing is shot after just a few tanks! Unless it had been lying around the shop for a long time before you bought it and moisture and rust got in there. That has been known to happen.
Keep at it! The OS 140 is a great pattern engine. Both mine have the Mintor 3M 140 twin head, which really helps the mid range transition and lowers the compression slightly, giving a wider sweet spot.