Re: Bosch sms4452gb
They are not designed to need lubrication so there is a problem with it. Very occasionally the primary gear slips along it’s shaft and doesn’t mesh correctly with the next gear. You can check this if you can very carefully remove the small drive motor and look at the cog on it’s drive shaft…try and work out if it’s still aligned with the corresponding gear in the gearbox, and if it has moved then some very gentle taps with something soft-faced like a screwdriver handle should tap it back on. Be aware that if you tap it too far it will be nigh on impossible to move it out again 😉
Failing that you have nothing to loose by using WD40 but ultimately you would need a new timer.