INS 9 - 1 deletes added waypoints

[Prof_Plumpy]

Doing a VHHX to RJTT flight. 

Diligently populating the INS with the next way points after 9.  They all happily show up on the minimap in the centre console. Entered in all new way points 1-6. 6 being the last point needed to get to the ILS.  

When the INS flicked from 9-1 it deleted all the waypoints and reset them to 0000N 0000E.  Had to quickly re-enter the deleted 6 way points.  What did I do wrong? Not using GPS or any other function.  

So now we are following the INS but for the life of me it would not hold an altitude.  3000 set, 2500-3200 given.  She was all over the place.  Its hard to believe that the first plane that could do a Cat-3C autoland has so many issues holding a set altitude.  Or following an ILS. Or over flying a VOR without trying to do a 180 turn.  With each new 'update' there is a plethora of items that break.