The dealer cannot find a fault or replicate the problem. Has anyone got an idea why this is happening.

No, Get a new bike

if its a fault steering lock, dont take no for an answer.

Are you taking the keys out?

Does the steering actually lock ? ( This is virtually impossible )
Or is it just loosing its power steering ( you can still steer but it will be harder )
If it is the latter it could well have electric power steering which is fitted to a lot of modern cars. l have seen this fail many times and normally needs a new motor to fix the problem

You have an appallingly bad dealer then. Your car is under warranty & the fault is potentially very dangerous as it might deteriorate to the point where the steering locks whilst you're moving.

If the steering actually locks, then it is most likely a fault with the steering-column lock & the only way to investigate is for the dealer to remove it & check both the lock mechanism & the steering column assembly. A trustworthy dealer would replace both as a matter of course even if they could not trace the fault; it could be due to one part being machined out of tolerance.

Complete removal, careful measurement & inspecting the parts afterwards for tell-tale witness marks is probably the only way to get to the bottom of this, but it can all be done at leisure by Honda engineers after replacement components have been fitted to yours.

Do not take no for an answer! Either give the dealer one more chance or take the car to another Honda dealership. Like all ultra-reliable brands, I've found some Honda dealers seem to have forgotten how to handle faults but others have been exemplary. If you're in the UK & in the South East, send me a personal message & l will tell u which Honda dealers I've found to be useless & which ones have been outstanding.

You will also find that complaining strongly to Honda directly will work wonders. The last thing they want is adverse publicity about their reliability or customer service.