INS Randomly Loses Track

[samb118]

HI iv had a lot of issues with the INS losing its track. iv tried loading the waypoints from the PFB to see if that sorts the issue but it still happens. it happens at different times in flight sometimes happens stright away, sometimes can be 5 hours into the flight. All three lose track at different times aswel but i dont know of to tell the autopilot to track off INS 2 with it happens. the INS controls still work all lights light up when i set it the dail to test but i cant enter any new coordinates and the hold button doesnt work so cant reset the position any help would be greatful. 

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