Tires: Tire only leaks when mounted on vehicle and in certain position., clock position, o clock

Question
I bought a used Focus back in March. A week or two later my tire went flat. I brought it to a tire tech off the vehicle and after a full inspection found nothing no leaks. Lets just say it has gone flat on me more that ten times since March and that is with the use of fix it flat. Long story short I have since taken it two other times to different shops both mounted and unmounted on the vehicle with no luck. All the shops have always dunked the tire including unmounting the tire for visual inspection. Today I found the leak after pumping up the tire and spraying the tire with soapy water, and have marked it with a white crayon. I will dismount it in the morning and see what can be done. I have long suspected that the position of the tire with the full weight of the vehicle was what was causing the leak. I have explained my theory several times to several tire shops and they all think I'm crazy. I am asking this question to see if you have ever heard of this before. The leak I have found is a small enough that you can't see without soapy water but fast enough to be flat some hours later. Here's the deal, I rolled the car until the hole that I marked was at at 12 o'clock position and it did not leak anymore. when I rolled the car and had the hole at a 3 o'clock position it leaked. This explains why sometimes the tire took weaks to go flat and others just over night. By the time I get a response I am sure a tire tech will have checked the tire with this new discovery about my tire. But I am asking this question to see what you think as I was once a tire tech and this puzzles me also as I have never heard of a small leak only showing up when positioned on the vehicle a certain way.

Answer
Brian,

It might help if you told me the location of the leak on the tire - center of the tread, lower sidewall, etc - and then I could fill you in on what is happening to the tire itself.

But without that information, all I can tell you is, I know that it is possible.

But the bigger question is:  Has the tire been repaired?  What did they find inside?