I took the lens out to clean it & I noticed a small magnet on the side of it. I’ve taken the lens out before & didn’t see a magnet.
I don’t know where it came from inside the printer head or how to put it back in.
Has anyone else had this happen? If so, how did you fix it?
Thank you for your help.
I have never seen that before. 
The only part of that head I haven’t seen the guts of is the focusing mechanism. I could be wrong, but I don’t think that small magnet is part of the head assembly.
I would remove it, reinstall the lens (cup goes up) and see if the machine operates normally.
Oh, and Welcome to the community!
Not in the mood to run down and pull my lens right now. Maybe someone else can look inside with a light.
Has to be some sort of magnet in the head to hold the lens in place. Design wise it could be two or more of those on the sides of the lens path. Something weak since the lens removal tool needs to be stronger. Don’t know.
After an inspection with magnification my guess is the retaining magnet is another ring in the seat of the lens cradle. There is no sign of a small disc magnet like that visible anywhere in the lens bore.
Are any of the hold down magnets on the head or where it rests on the gantry missing? That is super weird i have never seen anyone find a magnet there before.
Okay, so it looks like there was a magnet from another project that somehow got into the machine or onto the lens tool (I’m not entirely sure which). The lens snapped right in, I’m going to do some test cuts to make sure everything works right.
Thank you for all your suggestions & help.
Chuckle! I find those little things all over the place…I’m not surprised! 
Welcome to the forum! It appears that the magnet you found is not a part of the printer head assembly. Please proceed with some test prints and let us know how they turn out. Thanks!
I did some test cuts & everything seems to work.
I still have no idea how the magnet got there.
Thanks for letting us know, and I’m sorry for the confusion. It’s likely that this small magnet may have snuck in before your Glowforge was shipped. Please don’t hesitate to reach out if you run into any other trouble. Happy printing!
