K40 Tripping 20 Amp GFCI Outlet

[Baffled]

Hello!
I have a K40 Hobby Laser that I use infrequently to cut & egrave with.
It is driven with the Moshidraw software and controller via serial cable not USB.
I purchased it used approximately two years ago and I do not know how much the previous owner had used it?
Recently I wanted to use it to cut cardstock stencils for a Halloween costume, but when I made my initial test run and was adjusting increasing the laser intensity with the knob, the machine tripped the 20 amp GFCI outlet that it was plugged into.
I installed the outlet when I purchased the laser and it has never tripped before.
To verify that the outlet was not defective, I plugged it into another 15 amp GFCI outlet and it too was tripped when I increased the laser intensity.
I was able to only fire the laser with a very low intensity, so low that it would only burn an outline of the lettering an not cut thru a regular piece of plain printer paper.
I did open the back cover while it was operating and did notice that only the center of the output end of the laser tube was glowing ... I have never looked inside this compartment before, so I do not know if this is normal or not?
If you have any suggestions regarding possible solutions to this issue I would greatly appreciate any assistance.
It may simple be that I need a fresh tube, but I do not know?
In advance, Thank You for your time!