Leak only inside the tire I have a tube with a Schrader valve, previously repaired (twice). I needed to use it, so I inflated it by hand until it ballooned to 2x the size, search for leakages in water (valve too) and let it all night to check for slow leakages, but none were found. Later, I put it inside the tire, inflated it by hand (~15 psi) again, put a little soap in the valve, and went to check my email. Ten minutes later, it was totally flat. I repeat the whole procedure twice and it was the same story: the tire showed no leakage outside the tire but lost all pressure when inside the tire. (Finally, it blew out while outside the tire). Why is this happening? I'm just curious ...
Your tire tube is still subject to the basic laws of physics and logic on this Earth. If air is leaking out of it, then there is a leak somewhere and it is perforated.

There is probably something in your tire causing the damage, especially if this continues to happen. It's also possible that the leak was close to the valve, and whenever the valve was up against the rim of your wheel, it was bent just so to allow the leak.