Fenix 6 sapphire and hrm pro plus!

Hello everyone!

I own a fenix 6 sapphire and the hrm pro plus. At first it was great, there weren't any problems, then the running dynamics stopped showing and the heartrate stopped being accurate. I tried everything the manual suggests but nothing worked out so since it was still under warranty I got my strap replaced with a new one. The thing is I still have the same problems. No running dynamics, sometimes they don't appear at all, sometimes they partly appear. No power data at all and the heart rate drops all of a sudden. What else can I do? I feel like I am the problem at this point. 

Please help!

Thank you.