Mercedes nox sensor

Don’t visit the site regularly but just logged in to post my issue and starting having a read it seems like I am not the only one with lots of faults only thing that really gets to me is my dealer has not managed to fix any of the issues to date and the van is now out of warranty so they will not be getting another penny out of me for servicing or should I say checking nothing.
But now to my reason for this post ,has any one with the Merc 316 had any faults regarding exhaust nox sensors .
On our first trip away this year after lockdown and removing cover after 8 months the EML came on after about 100 miles ,took it straight to the nearest Mercedes truck dealership to be told it was down  stream nox sensor that needed replacing ,and after discussing why at only 12000 miles but just out of warranty they suggested resetting the system and only charging  for diagnostics but after a few days it came on again .Have spoken to Mercedes customer care a couple of times with no success so far in them offering any assistance or good will . Now back home and have booked it in next week at my local dealership who tell me they will have to do the diagnostics again .Just wondering if anyone on this forum has had  any similar problems as it does seem to be common after reading lots of other forums regarding Mercedes car and commercials

If engine running normally, apart from warning light, then I'd suggest a good hard run of at least 100 miles, 70 on motorway, min engine rpm 2000, hard as poss to/from motorway/dual carriageway.

If, after that, then it needs to be fixed, sorry.