I've got a screw loose...

or rather, displaced!
Yesterday my Canon 7D started telling me that it couldn't communicate with the battery, either of them!
Who knew you could talk to batteries, perhaps I should try it...
Googled the fault and it turns out it is really common.
Some people suggest putting the camera in the freezer - dumb idea!
Lots of people say it's because a circuit board retaining screw comes out and lodges somewhere it shouldn't be.
Found a YouTube video.
Took the bottom off the camera (scary) and low and behold, there it was.
Or, rather, wasn't!
Found the culprit - extra - wedged further down.
Refitted it, reattached the bottom, refitted all the batteries and the battery cover, reset the clock and...
Bingo, it worked fine.
That saved me around five-grand!
Now, what shall I spend it on...