I not so recently and reluctantly offered to check the non-operating cruise control on a friends early '80s Mercedes 180E.
The problem appeared to be some bloated and leaking electrolytic capacitors - standard values that I had in my parts stash. All is good, so just replace them.
Well, my solder station(50W +) iron just sat on the solder unless I maxed it into the red and even then it was slowish working. I should have stopped there(out of practice) and found someone with a more powerful iron. I got the caps out OK but also lifted/removed PCB tracks. Board ruined.
I suspect these control boards were early production lead-free solder items.
After a very long time scanning Ebay, I picked up a used working replacement from the US for $AU70 delivered to Oz(vs 250 to 350 usually asked).
I couldn't charge my friend for it as it was my fault that the $2 job was ruined.
Lesson: soldering PCB components is a quick on/off discipline. I got lulled by non-pcb guitar amp building.