Thank you, 
I will try that FlyTo-update even the unbound is working so far great now. Also will check the voxelSize and AutoCorrection. I will let you know if finding something.
This was the crash when I didnt use the checks if the destionation is suitable:
[2017.03.17-22.36.52:768][806]DoNNavigationLog:Error: Destination X=340282346638528859811704183484516925440.000 Y=340282346638528859811704183484516925440.000 Z=340282346638528859811704183484516925440.000 is outside world bounds. Please clamp your destination within the navigable world or expand world size under settings if necessary.
[2017.03.17-22.36.57:709] 67]DoNNavigationLog:Error: Pawn’s initial position overlaps an obstacle. Pathfinding will not work from here, pawn needs to move to a nearby free spot first.
[2017.03.17-22.37.00:565] 67]LogWindows:Error: === Critical error: ===
[2017.03.17-22.37.00:565] 67]LogWindows:Error: Fatal error!
[2017.03.17-22.37.00:565] 67]LogWindows:Error: Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x0000000c
[2017.03.17-22.37.00:565] 67]LogWindows:Error: UE4Editor-DonAINavigation.dll!ADonNavigationManager::SchedulePathfindingTask() [d:\build++portal++full\sync\localbuilds\plugintemp\hostproject\plugins\donainavigation\source\donainavigation\private\donnavigationmanager.cpp:2084]
[2017.03.17-22.37.00:565] 67]LogWindows:Error: UE4Editor-DonAINavigation.dll!UBTTask_FlyTo::SchedulePathfindingRequest() [d:\build++portal++full\sync\localbuilds\plugintemp\hostproject\plugins\donainavigation\source\donainavigation\private\behaviortree\bttask_flyto.cpp:107]