Problem with Donner today. Laser cuts had less power and looked like calligraphy.
I replaced the lens tube with the one from Blitzen. That fixed the problem - laser beam was catching part of the tube. The tube from Blitzen had a wider opening.
New problem - Blitzen lost power. It’s laser beam was catching the now narrower tube opening. I found a wider opening lens tube cap in the supplies and switched it. Fixed the problem.
Though both lasers are now working, I think the better long term solution is to fix the mirror alignment on the lens tube.