Trend T5 router - intermittent speed wind down

[beekeeper]

Good evening Uk Workshop - I am a relative newcomer to the delights of woodworking kit and I should be grateful if someone could offer me advice on an intermittent fault on a Trend T5 router which I have recently purchased second hand. Whilst in use the soft start motor will wind up normally and then run OK - but intermittently the motor will wind down, often to a stop, and then after a couple of seconds wind back up again to the selected speed. This despite the machine being switched on throughout the fault occurrence . I have read some comments that the speed controllers in T5s can be suspect, could anyone advise please?

Thanks