Heart rate/calorie count not registering

My 255 is not registering a consistent heart rate or calorie count. 
Ive just purchased this as of 4 days ago and the 3 work outs I’ve done it’s not reading info properly at all. 
As soon as sweat is introduced it gives up and doesn’t track heart rate. I’ve bought this watch to track gym workouts and daily calories as well as monitor my over all health but I’m finding it very hard to trust. 
I’ve shaved hair off where it sits so there’s no interference. I’ve worn it tighter. I’ve worn it looser. 
I’ve got 3 clear points where you can view on the heart graph where it just stops counting and even after wiping is showing the wrong data. I can have a 130bpm and it will show 70. 
I even noticed during the day I can look down and it just doesn’t register a heart rate correctly. 
I want to know if this is watch issue operator error or just unlucky because I’m seriously considering returning it 

Thank you in advance