search for OVP there are many posts on this little device. something in one of the posts might explain your problem exactly. do a search and look for the part numbers of the older and newer part. If you have the older one, look into replacing it if you suspect it is the problem.
Others have had stalling problems etc, and the ovp was the culprit in a lot of situations, but not all.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.