“Nearest point on route” does not play very nice in combination with “automatic recalculation”.
See this demonstration from @grua
May I suggest to replace it with something different:
Let me call it “nearest point on route +500m”
The idea is to place the “point of rerouting” a few 100m closer towards the end as the exact “nearest point on route” would be.
The moment you leave the route, the nearest point is exactly the place you’ve just left .
But usually you don’t want a rerouting back to the place you’ve just left.
Hence the idea to add a few meters towards the end.
Manfred