Funny enough I tried (dt*12000) before, I figured it would be necessary otherwise the calculation would do different things.
Now with that (dt*12000) the turning is smoother, however it still turns very fast. It does seem to be smoothed though, it's just that it makes its turn within a blink of an eye. Ah yes, it also does a weird rotation around its own axis just before it heads to a waypoint. Also happens in the blink of an eye.
I'm not sure what the framerates are on my devices, can I add a code for that in Construct? Anyway, I used to have a 6 year old PC, which at the time was already made out of second hand parts mostly. At that time I used a 60hz monitor, currently using a 144hz one with a very fast all new parts PC, built it about 9 months ago.
As for the game, when I run it on that new PC, in debug preview it says I get 140-144 fps. It seems that the engine is limited to what your monitor can render?