Not only that, you can lift a defective tube right out of its shipping crate.
Do a test to verify TEM00 resonance at 30% power or so. This lengthy thread covers the territory:
You want a scorch on paper, not a hole torched through, so set the pulse power and duration from the KT332N display:
Then the Pulse button on the display will do the same thing every time and you can adjust the time & power for useful results.
Glass is tricky, so see how it behaves on paper.
However, glass CO₂ lasers typically do not fire below about 10% of their rated power, so it’s surprising the previous tube did anything at 5%.
And if these are new glasses, then the material will almost certainly be different and require some fine tuning.
My guess remains a bad tube, though.
That’s going in the wrong direction, because the focused spot is typically around 0.2 mm = 127 LPI. Using Line Intervals much less than 0.2 mm (or much more than 127 LPI) overlaps each trace with the previous one, which can lead to overcooking & cracking the glass.