Some additional information to help with the understanding of the issue:
We just received our first iPhone 4 replacement from Apple (see https://forums.macrumors.com/threads/949231/) and the same symptoms of dropping signal when touching the lower left black band exist on the replacement.
After getting a feel for how widespread the issue is, the most we were really hoping for was a chance to see that this might have been an issue only with a batch of iPhones (which it still may be, this can't confirm that). If the issue was corrected in the replacement at the same location, then that would have confirmed that it was an issue with certain iPhones but not others.
Our collective intuition is still that it is an issue with the hardware design and a number of other factors either exacerbate or prevent the symptom (or the degree of symptom from occurring), such as proximity to the nearest tower/strength of the signals from towers.
We just received our first iPhone 4 replacement from Apple (see https://forums.macrumors.com/threads/949231/) and the same symptoms of dropping signal when touching the lower left black band exist on the replacement.
After getting a feel for how widespread the issue is, the most we were really hoping for was a chance to see that this might have been an issue only with a batch of iPhones (which it still may be, this can't confirm that). If the issue was corrected in the replacement at the same location, then that would have confirmed that it was an issue with certain iPhones but not others.
Our collective intuition is still that it is an issue with the hardware design and a number of other factors either exacerbate or prevent the symptom (or the degree of symptom from occurring), such as proximity to the nearest tower/strength of the signals from towers.