These must be some bum sets. I use them all the time with iPhone in my pocket mostly the back pocket. I also use with my Apple TV and they never stutter or lose connection. I have even gone out of the room to the kitchen downstairs and they don’t stutter.
Around the house, with my laptop, or with the Apple TV, mine also work great even into other rooms, but outdoors with my phone in a pocket they are really bad, just as others describe. Work fine from the Apple Watch though, but that’s not in a pocket.
On my second set, with no improvement. Have tried 3 phones (7, 7+, 8), completely reset phone, tried 2 different watches (Series 0, Series 3 LTE), worn no watch. It’s maddening. They’re pretty much worthless.
Apple told me it was simply interference and I was on my own (interference from what? My Apple Watch?!). I had to threaten to throw them away and just buy another set before they replaced them, but they started breaking up within 20 minutes walking outside. Seems some people got lucky after a few replacements, but I hate to stab in the dark like that when each replacement is hours out of my day…