DMF is part of the clutch assembly, and I'd be astonished if it threw up a fault code for a turbo.

When you had the turbo re-built, did you have all the pipework replaced too, or was it done 'on the cheap'? If it was done cheaply, then not really surprised if it's gone again, as the oil feed pipes were probably well carboned-up, and the old (and new) turbos would have failed due to oil starvation.

completely unrelated faults.

Its unlikely a fault code will directly detect a faulty/worn/knackered turbo since this is a mechanical unit, it will detect a problem with the boost pressure from the turbo instead which in turn could be caused by a number of things, (split hose, faulty wastegate, boost pressure sensor, turbo itself, etc)