Hi all from northern germany, yesterday i take my old polar crossing chart and simulate a polar flight with the wounderfull PMDG777 from ENVA to PANC. Thanks Team from PMDG!!! the route was: PANC GISOX N70E007 N76W000 N82W020 N85W060 N84W090 N80W130 N74W141 N70W146 TKA Panc.and no winds clear skys. the flight endet with no FScrash. when passing GISOX i change to the TRUE heading. after N70EW007 the GRID sign comes to the ND. the flight was on LNAV and VNAV and FL380. the 777 shows the TRUE and GRID heading. but at the waypoints N82W020 N85W060 N84W090 around 10 miles before we passing the points the 777 lost the correct heading and fly 2,5 miles left then right of the route. then the plane courve back to the flightpath. My Question: what i doing wrong with this great plane on my polar flight?? sorry for my bad english! greetings Kalle near EDDW