I looked after a friends Mk3 2018 650 Versys whilst he was out of the country.
It had an intermittent fault that was a pain to solve, as you described it was a lottery if it fired up 1st time.
The bike was left with Millenium Motorcycles in St Helens, Meresyside (01744 616161).
I explained that there was no hurry in returning the bike, but could they solve the issue - they did.
But, I don't wish to mislead you with the fault they found.
However, it came down to a wiring fault that resulted in the ignition switch being replaced.
I would suggest you give them a call and ask for Gary in the service department.
Gary may be able to recall the exact fault on Mohamed's green 650 Versys, that they had in the shop for a couple of weeks in June last year.