Hi HayterNovice, and welcome to TGMF..
It's likely to be one or both of the rollers dropping out of drive as you mentioned. You can usually see them slipping by holding the machine slightly up by the handles, engage the drive and slowly lower it to the ground observing the rollers, see if one of them is stopping.
What is the model of your harrier? (On the silver sticker, example 490D).
It's likely to be one or both of the rollers dropping out of drive as you mentioned. You can usually see them slipping by holding the machine slightly up by the handles, engage the drive and slowly lower it to the ground observing the rollers, see if one of them is stopping.
What is the model of your harrier? (On the silver sticker, example 490D).