Its almost more than 10 months since (2.20.03.x) the no channel preview issues showed up on 322, 349 and 351 boxes. Looks like we have no solutions from Infomir yet.
a) Boot setting change from NADD1 to NAND2 solution NEVER worked.
b) "CHECK WITH YOUR PROVIDER" is not an option as it seems like that has nothing to do with it.
Please let us know if you any other solution i other than the above two answers?
If immediate fix is not available please at least take care of this in you next firmware update. The last one was on May 31, 2018.