Dermapen cutting like a blade?

[ccml]

Hello people.
I have been recently experimenting with my new dermapen.
I have used it at 1.5 mm with no problems, but today I tried 2mm, and it cut my scalp like I was running some kind of blade.

I feel that the reason may be that the vertical movement of the needles is not wide enough, so the needles are not completely leaving my scalp.

I would really like to know
1) if there is any other possibility for the little accident
2) if its a problem with my dermapen or with my cartridge
3) if this kind of wounding would have a negative effect on my hair growth

I leave a couple of pics of what I'm saying. The needles only come out of the borders of the cartridge if I set them at about 2.5mm, so I put it in that position in mode of illustration of what I'm trying to say.

I'm waiting for some advice of the more experienced folks.
Thanks a lot!

EDIT: My dermapen is a generic one, sold under the name "Dr. Pen Ultima N2" (shows up on amazon if you google it up).