[solved] 5D Mark III v.1.2.3-ML, Eyefi once used, SD-Slot now unusable

[Ronny]

Hello,
I used to use Magic Lantern (Version unknown, Nightly Build about a 6 months old) without any problems with dual writing of my RAWs to SD (SanDisk Exteme)/CF (SanDisk Extreme).
ML on CF.

I wanted to copy some Pictures to another SD-Card, inserted the card of a friend (which happened to be an Eyefi-Card) and went on - no problem. Card detected. I even saw the special Eyefi-Menu and wondered about those functions. Went on and copied pictures to the Eyefi-card.

I removed the Eyefi-Card and wanted to put back my Backup-SD-Card again, but the camera won't recognize ANY SD-card anymore from that point on (we tried several different cards - non-eyefi, eyefi back again and so on)! I removed everything, battery (a few minutes), changed cards, removed lens, used different batteries, nothing changed.
I didn't know before about possible problems with Eyefi-Cards.
I tried to uninstall ML (removing the bootflag), but situation hasn't changed 

Before I try to overwrite the main firmware with the new version 1.3.3 as a last try (and say goodbye to ML) is there anything I can try before??

Every help very much appreciated! Can't believe I damaged my  camera with ML/Eyefi combo 

[a1ex]

Are you able to use CF cards? (I assume yes, since you were able to uninstall).

It might be a problem with the SD card contacts. I have this problem on 550D (card slot worn out), and to use any SD card, I have to stick a piece of cardboard on the back of the card.

Can you start the camera from a bootable CF card, with a formatted SD card in the slot? If so, we can try to troubleshoot it (at least we can see in detail what Canon firmware is trying to do with the card).

FYI, I'll be offline for about one week.

[Ronny]

Hello A1ex, thanks for your reply! I already carefully looked inside the slot, but can't imagine I stressed the pins too much :-O
I can start with CF, ML was running while I couldn't access the SD card. Would be great if you could help me troubleshooting this!

[Ronny]

Solved! At least it doesn't seem to have something to do with ML since all of a sudden today the slot repeatedly worked. Leaves mixed feelings about my backup safety though...

[a1ex]

Yay! May I ask what the problem was?

[Ronny]

I don't know, what the problem was - therefore my mixed feelings.

I described, how the slot was from now to then unusable - the only reason I could imagine were ML/eyefi problems, since I nearly never ever used the sd card slot to that point. I tried again a few days later - still didn't work (I also tried to fit the sd card in another way, rattled a bit, wondered if something would just be loose, mechanical problems - no success).
Now, just hours before I wanted to send the 5D3 to service (the day I realized I had a few days warranty left), I inserted the SD card again, at first same error again. But with the second try and every other time afterwards it just worked as expected 
Now I don't know whether I should send in the camera (also not knowing, if this falls under warranty?) or just hope (I hate to "hope" my backup-system works) that the slot will work most time I stick in another sd card...