Today I realised there’s an issue while using touch lock. I was using a hat and was adjusting the right unit a tad. Only touching the sides of the unit, not the touch area. The hat however brushed against the touch area. Right away the sound got lower, almost muffled. It sounded like something had come between the speaker and the ear canal, muffling the sound. I took up my phone to check volume, since I had touch lock activated, but saw it was still on max. I lowered the volume manually and then raised it back to max and voila problem fixed, sound was again clear and louder.
This happened quite a few times throughout my time outside. I tested a few things and realised it was enough to simply pull at my hat a bit so it moved across the touch area and the same thing happened. Using my fingers on the touch area did not recreate this issue however.
I use an iPhone 6s and latest firmware.