Engraving is getting dimmer after a while

I’ve received the new laser I purchased. It’s a 90W RECI W2 laser. I initially thought I had bought the best, but now I think I might be one of the unlucky ones…

It turns out it has what I believe to be a defective laser beam, as it outputs a laser beam in the form of a disk.

I will open a new topic for this issue, as it is a different one, but I’m not closing this one for now because I have not yet verified that the milliamps don’t drop anymore.
This is the post: 90W RECI W2 laser tube outputs concentric circles