There was a recall on the early 850's where we had to access the soldered connections for the front abs sensors, cut them out and re-solder them. This may or may not be your problem, the typical symptoms for this were at low speeds 0-15 mph the abs would modulate. These soldered splices are located in the harness underneath the main relay/fuse panel. Although it does sound like the problem we had way back when with these cars it does seem a little odd that it is cropping up now as most of those splices went bad right out of the gate or shortly thereafter. To have one go 11 years and then start acting up seems strange, unless someone did a piss poor job on the recall 10+ years ago.