Misshapen inner tube, is this evidence of it being incorrectly fitted? I recently fitted new tires and inner tubes (Continental 700 25c). Today I had a fairly slow puncture, going flat in around 20 mins. I removed the tube and found that the puncture was at the edge of what appears to be a defect in the surface of the tube, at the point where the top seam meets the edge of this apparent defect.



Is this most likely caused by the tube being pinched or folded somehow when installed? I'm guessing that I've done something wrong here, rather than there being any issue with the tube itself.
Would you have scratched the tube, it wouldn't have taken 20minutes to go flat (95% of the time you simply cannot inflate a tube that is scratched during installation).

This is mostly some sort of storing issue, you usually got that when hanging your inner tubes on a hook. It's a rather common thing to observe in second-hand tubes that don't go directly from the box to the wheel, the rubber get compressed and once inflated you get this weird look.

Or you can, but it's rarer nowadays, have this in a brand new tube, just being caused by non homogeneous rubber distribution, it happened to me sometime ago.

Most of the time and from my experience if the deformation is not to pronounced (and it does not seem that way here) it should not cause any problem since the inflation will simply fit the shape of the tube into the tire.

It's uncommon but with bad luck the deformation could cause a hernia to happen but then again with a hernia your tire would have not taken 20 minutes to go flat (usually goes boom and flats out in 2 seconds).

I would go with deffective tube rather than wrong installation here.