I know this is an old thread but I believe I had the same issue, and VW repaired it.
A couple of months ago while driving on the motorway, yellow coil light suddenly started flashing and I had "ACC & Front Assist Err." come up on the display. GTD went into Limp Mode and I pulled over onto hard shoulder. Came up saying Start/Stop Error too and wouldn't shut off automatically. I turned the ignition off and on again, car started absolutely fine and whatever problem there was seemingly disappeared.
I took the car too the dealership to get it checked out anyway, they did some diagnostics and apparently found a fault code regarding the fuel pump pressure. They didn't say how the two things could be related, but the fuel pump was replaced. Problem has not occurred again.
I'm having the exact same problem. Only I have to confess to having the revo stage 1 remap and wonder if this could cause the problem! a solution is needed asap as I am sick of seeing the light!