Very slow wifi when bluetooth is enabled since iOS 10

Hi all,

since the update to iOS 10, the download speed of my wifi (2.4GHz) on my iPhone is very slow when bluetooth is enabled.

When checking my connection speed using the speedtest-app, I get around 5000kB/s with bluetooth disabled and around 50kB/s with bluetooth enabled. In fact, I can see my download speed drop instantly when enabling bluetooth during the test and increasing when disabling bluetooth. The iPhone is connected to an Apple Watch via bluetooth.

Upload speeds are unaffected and stay constant at around 300kB/s (limit of my connection).

My iPad connected to the same network (also running iOS 10) does not show this behavior.

I called Apple Care support and they told me to rest my network settings and reset my router which I did. This fixed the problem only temporary; one day after the "fix" the old behavior returned. Now they are telling my the only option might be a reset of the iPhone to factory defaults which I would like to avoid.

The issue started with the update to iOS 10 and did not disappear after upgrading to 10.0.2.

Anyone else experiencing this issues or any clue on how to fix this?

Thank you!