Has anybody any advice. please, on how to stop my Tyme Cub motor cut-out switching off the power after only a few minutes ? I've tried using a vacuum cleaner on the ventilation slots but they didn't look blocked and the motor doesn't seem that warm. Are there any user-replaceable bits (brushes ?) that could cause the problem ? I don't want to splash out on a new motor or control box if it's something relatively simple. Thanks for any pointers.