It has been doing it for some time.Welcome to the forum - that's not a model I recognise, any chance of some photos (inside & out) as it may be a rebadged version of another machine?
Has it always done this or just started recently?
Thanks for the suggestion, will take a look at the contactor to see if arcing has occurred.Looking at the diaif arcing has tarams It seams to use a pair of contacts on the contactor to short the motor out when the trigger is released. It could be that the contacts of the contactor have arced and burned and so are not giving the short to stop the motor from running on. The contactor should have a part number (s) on it that may allow sourcing a replacement. It MAY also be possible to take it apart and clean the contacts (probable not an easy job ? ).