Wahoo heart rate monitor interferes with the Apple Watch Heart rate sensor

I use a Wahoo TICKR monitor for running. A chest strap is best when running in the winter since the apple watch sensor does not like cold and dry wrists.

The sensor works flawlewssly. It connects directly to the apple watch as a bluetooth device (not associated to the iPhone, just to the watch) and heartbeats are perfectly recorded in my activity.

The problem I have is after removing the strap after the run. The Wahoo goes idle, I can see that it is "not connected" in the Watch's bluetooth settings. But when I check my heartbeat using the wrist sensor from the watch, it shows a totally wrong heart beat (e.g. varying between 125 and 150 when I am actually at around 70).

Furthermore, while HR app shows the wrong BPM, the ECG app shows the correct BPM.

So I realized today that if I turn off bluetooth, or remove the Wahoo TICKR from the list, then the Heartbeat app reports the correct BPM.

That is annoying, since I like the Wahoo and it would be a pain to add/remove it before/after each run.

I made a support call but since this is related to a 3rd party device, it is unclear who's problem it is. But to me, a device that appears as "not connected" should not interfere with the watch.

[Edited by Moderator]