Did a little bit of testing about this one and it seems like there is a problem with flyby waypoints. Departed out of EDDW on WSN1M and EEL5Q, the fly over waypoints just work fine, but fo example when flying from DW090 to DW100 the 737 just starts to turn when its above DW100 and not before, but since DW100 is a flyby waypoint the aircraft should start the turn before the waypoint. And even after the turn the 737 overshoots the heading to DW101 to the left end just ends up trying to to a sharp right turn close to DW101 to overfly it(again a flyby waypoint...) after that the LNAV lost the flightpath completly...best workaround ist probably to do hdg select and select the next waypoint in the fmc.

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