Polar M400 - overestimation of steps

Hello everyone,

I was just wondering if someone else has the same problem with their Polar M400.

It overestimates my steps by 1000s of steps during the day:

it counts the followings as steps:
- knitting (movements of my wrist)
- petting my dogs
- laying in bed and moving my arms
- basically every movement I make with my arm

I did talk to someone from polar through a chat and twice on the phone and two said it is "normal" because it calculates steps through arm movements while the last representative was more understanding why I think it is frustrating and said he understands if I would return it.
How can a normal hand movement count as a step? I don't have any problems with my Garmin Vivofit.
I bought the M400 because I wanted to combine my Polar RS300X and Vivofit.

If it is a common problem I will return my M400, I just hoped that maybe it is just the one I have and I can just exchange it.

I am thankful for any input.