URGENT - 15amp cpu electronize problem

Everything is back together and working well on hornet 2 then today when testing one of the drill motors starts acting up. Basically it will move the bot forward very slowly but it will judder as it does and sometimes will kick into full forward as I am asking.

I have narrowed it down to the electronize by trying different radio gear (spectrum and 40meg) and different motors.

I have a feeling that the relay is sticking but I would like a second opinion before I head off to maplins tomorrow.

Normally if its a relay you loose direction control, ive not had the problem that you have tho.