Originally Posted by
FullWings
I’ve had this before and I think it might be due to software latching the incorrect datum (true/mag) as the above post. Recycling the HDG REF switch seemed to clear it on both occasions...
I tried recycling, it did go back to normal later, however as long as the anomaly existed, the 'latching' as u mentioned didn't change the heading scale as it should during the usual selection of the switch. The 'latching' (assuming that was the case) only modified my entry of bearing as 'true input' on Fix Page, and applied variation to it.
Right FMC Did the same.
Will look up the FOT bulletin but due to operator difference might not have. Will try googling.