Tdi 1.6 CR 105bhp 2014

I realise that the issue is an 'old chestnut' now but I bought my Rapid with the 'fix' already applied.

After DPF regens every 180 miles, regardless of driving conditions with Esso diesel and Archoil/Lucas/Millers etc added in turn (still 180-185 mile regens)

and sounding like a taxi, even with new Quantum oil and all filters (very clattery from 1200 - 1900 rpm under load in particular).

I am now going to have the EA189 rolled back to a 'pre-fix' state but have read a few horror stories about the ECU being flashed and then not allowing the 

pre-fix software to be written, but worse still, then not allowing the 'fixed' software to be re-installed either and cars being left stuck at the 3rd party tuners.

Is there in fact any truth in these stories whatsoever, or did VW put a block into the ECU at some point in time to stop the rollback/reversal and if so, has this 

practice now been stopped?