that makes sense,but how cant I know for sure
Is that your only M? If you have another with a removable cable, you could test with that cable under the same circumstances to eliminate the cable, and swap cables between Ms.
If not, it can be hard to test for an intermittent electrical fault. You could literally take a continuity tester and probe between the individual contacts in the SDL jack and where they run to the controller (I don't know which pins on the controller this would be offhand) and you may or may not get continuity, depending on the stress (or lack thereof) on the jack. These are the pins for the jack where they connect to the PCB, stolen from Sandy's website:
If any of those solder joints look dry/hazy or cracked, the first thing I would do is reflow them with some fresh 60/40 solder and a good flux so that each one is nice and shiny.
We're still grasping at straws here though. There are replacement controllers, including USB and bluetooth ones that you could purchase instead and just swap in, which would probably be the nuclear option. The very first thing I would do would still be to check for damage and/or oxidation on the contacts between the cable and the jack, and then the solder points on the PCB for the jack. If any of the pins in the jack look bent further than they should be, you could also try to bend them back into place with something like a hooked paperclip or dental pick. I have had to do that with laptop ethernet jacks in the past.
I also don't know what sort of problems are typical with M SDL jacks though. I'm sure fohat would.
