Thank you for the work you have done on this, however I am not so sure it's a flaw in the Simbrief Exporter. More I think, something to do with the Pro version of the CRJ. My reasoning is that the Simbrief flight plan format is the same as that used for the pre-pro version where this problem did not occur. As you know, the correct way to automatically import Simbrief flight plans into the FMC is via ROUTE, where the departure and destination ICAO codes are entered as one string - EGBBEINN. Of course, the entire flight plan can be entered manually into the FMC and I did this yesterday without getting the MSG.
So, although I very much appreciate your efforts to assist in this matter and your suggestion does help, I don't think we have got to the bottom of it? Something has changed and it's interesting to see that Forum member Marc has the same problem.
I have friend here in the UK who also has the pro version of the CRJ and who also had the pre-pro version. He does not appear to be having the same problem as me, yet we have compared CRJ windows folder structures and content and we are identical, which just adds to the mystery!