Solder joints are the weakest link in many PCB's.
Unfirtunalty MB have upgrader the box since the 2000 car and the box we ahve is sealed shut and the box can not be opened with a knoife as was detailed in the info i listed.
We did however find heavey corrosion once we got the 3rd screm off which araing had a revised told head on and not a cross headed screw. We had 3 5mm start bolts the bottom one had ceased solid and we ended up having to cut the head off. I took photos of the par and the curosion and will try and up link them once I can get my laptop back on line.
We have had to get the part from the dealer and are going to fit it outselves this weekend that alone cost us £759.00 UK Stirling Pounds!! Hope this fixes it. i would suggest fold to wipe vasaline around theres just to help keep water out and help prevent there unit going the same way. As well as around you car horns as these corroded away on ours and we had to replace them for £15.00. Vasaline acts as a water barier.
At present the car haas corrected it self again as it did last Thurs/Fri lasted 22hrs. So far I am close to 48hrs now this time with silcene once more. As I will be washing the car to day I expect it will be back!!