No I have not fitted one, but since going over the electrics, that is what it feels like.
I took it out in the wet last weekend and it started stuttering / missing / cutting out.
I found quite a few of the spade connectors were loose, so I tightened them up with a pair of pliers and pushed them back on.
Took it out a couple of evenings in a row and no missing, no more faltering, nothing but an absolute pleasure to ride.
If anyone is suffering intermittent running, take a look at the electrics...............