Daf LF55.220 won't crank turn over

Hi,
Occasionally last week my Daf LF 55.220 (2007 380k Km)refused to start. Turn the key and you just get nothing.
It is behaving exactly as it does if it is in gear (will only crank if it is not in gear), except it is in neutral.
The “N” is on the dash to show that it knows it is in Neutral.
I have been lucky enough to be on an incline and easily bump started it each time it has happened so far.
I am guessing an intermittent fault with the gear sensor. ?
It is happening more frequently now.
Stopped for a coffee on the way to drop it for a PMI the other day and it wouldn’t start again. This time on flat so couldn’t bump it.
Called Dafaid and as I sat waiting kept trying it. Suddenly started after about the 15th attempt. Managed to cancel the call out just in time.
Explained fault to garage who said they’d check gearbox sensor etc.
Of course it started fine every time it was with them and they can’t investigate a fault that isn’t there.
Collected, started up no prob, drove to yard, turned it off… and it wouldn’t start again :unamused: Typical
Kept trying and off it went after a few goes.
Now I guarantee it ain’t going to start at 05:00 tomorrow morning.
Garage suggested maybe a dead spot on the starter motor. i.e. worn brush not contacting if stopped at a certain point in rotation.
Can anyone suggest any other possible causes.
As always with intermittent faults it never manifests when you want it to.
Next time it happens will call Dafaid out and see what they say but of course there is every chance they’ll just turn the key and it’ll start no prob!
Any thoughts at all?

You need to eliminate the starter motor. There is more than one way of doing this. If safely accessible and certain the vehicle is not in gear & cannot move and not prevented by a terminal block, you could carefully short the positive to the solenoid trigger terminal (either with a length of insulated wire or a screwdriver with an insulated handle) when it will not start. Or before you have trouble you can run a wire into the cab with an in-line bulb in the trigger wire so that voltage can be seen to get to the starter, or not, when there is a non start condition. If the pinion does not return fully to its rest position (clutch dust) then you will get a similar condition to that the garage has described.

Thanks for your input.
Started no prob every time yesterday fortunately.
Yes, I can try shorting it directly.
The clutch dust on the pinion is one I haven’t heard before so thanks for that. Wonder if it might just be that. Give starter a few knocks with a block of wood next time. I’ll see how it goes.
Thank you.