iPhone, kept iPhone in house using the Internet and walked around backyard to determine WI-FI range ⇒ perfect performance from headphones.
Next test, placed iPhone in pocket still using Internet and walked around backyard ⇒ total erratic performance from headphones.
Are headphones defective or are Blue tooth latency's to be expected ?
If you were listening to downloaded content, I got nothing.
You’re dealing with 2 different things here.
1) Bluetooth connectivity of your headphones to your phone.
2) WiFi connectivity of your phone to your router.
Sounds like the headphones are fine. You’re just exceeding your router’s WiFi range when in the yard.
In the first test your phone remained closer to the router. This has nothing to do with the headphones.