The plot thickens. I've been speaking with some repairmen, and the other issue mention regarding possible focusing issues is if the lens elements were swapped out with a different 'flex at some point by a previous user or repairman.
Sure enough, a quick serial number check reveals my Rollei, No. 1219317, is a MX with 75mm Tessar-- however that model number should have a Tessar Jena lens. My example has an Opton Tessar. Perhaps I'm incorrect, but I assume the serial numbers don't lie, and that there shouln't be any No. 12XXXXX models with anything other than a Jena on them.
Does any body have any experience our thoughts on this issue? Am I (as I fear) starting to enter lost-cause territory here?