Somewhere there is a list of modest priced parts to change out on the board if your problem is not gone. I supect they are dried out capacitors mostly. Might be in the archives. Since you are bringing home solder wick from work you could probably cope with the changes. These are known failure items and as I mentioned really cheap if you have a good source. I have always wondered if the heat going up the component leg has reactivated some old part or if it is indeed just poor solder connections. I guess it could be the result of a poor wave soldering bath at time of production leaving a lot of marginal connections as well. It only takes one cold type joint to upset the apple cart. I wish there were schematics around for various mercedes modules. I suspect they would be very easy to troubleshoot with extension harnesses. They just want too much to recondition them. I repaired an idle control unit last night that had a rebuilt sticker on it from years ago. 1985 126 380se. There was some evidence I re repaired the original failure mode again. No active shorts but just a voltage divider network gone open. Almost like the original resistor sizes were not quite robust enough to go the distance. Will submit it to an active test in the next couple of days but should be okay. This module is pretty expensive new for what it is.