After the bottom bracket issues on the single speed I ordered a new FSA Platinum ISIS bottom bracket to replace the failed RaceFace SRX. This evening after a shorter than expected Christmas I fitted the new bottom bracket and now the drivetrain is working just as it should. Installation went smoothly and after cleaning the chain and slightly readjusting the tension it’s ready to ride.
Now to wait for spring time to come and single speed weather to begin again… Or maybe my neighbors (spanning the four miles to River Bends) will properly clear their snow…