This is not a problem, just a curiosity. Whenever I took out my APP, as soon as I removed the first bud, it sounded on the other ear like something changes. Even with no audio playing through the buds, it’s just as if the other ear becomes a bit muffled as soon as that first bud goes out. It happens regardless of which bud I take out first. This is on APP2 with USB-C. It’s been this way since APP1 and across different iOS and macOS versions as well as various APP firmware updates. I usually have Transparency set so I knew it wasn’t ANC related. I also in Accessibility do not have ANC selected with just a single bud.
For the longest time I was left wondering what the APP were doing…
Until just the other day I finally figured it out. By chance I had the APP settings open on my iPhone because I was tinkering with something else when I got called away. So before I run out I pull the first bud out and right before I lay the phone away to free up my hand to grab the APP case I see how the toggle switches from Transparency to Off. And right then and there the other ear becomes muffled. Later playing with that toggle, sure enough, the ‘muffled ear’ is the result of no Transparency — I guess demonstrating just how good that silicone seal is.
So bottom line, whenever you take out one bud, APP automatically turn off Transparency mode and that’s what leads to the change you hear on the remaining bud. Not a big deal of course, but figured maybe somebody else had also been wondering.