Garmin HRM Soft Strap issue

During a ride, initially my Garmin hrm strap works perfectly.  But 1/2 hour into the ride the HRM will suddenly drop to 76 beats per minute and stay there for the rest of the ride.  I know my hr has not this dropped significantly due to soft pedaling,  because I am usually about to vomit all over my bars.

I have changed the battery.  

Anyone else having this issue?  I am going to pick up a ant+ extension cord, but was wondering if it might be the Garmin HRM.  



The same thing happened to me. I also thought it was the battery. I changed the battery but have not tried it yet if it works. Using a garmin hrm strap to.