Ross, that's a simple tickle adjustment, not a problem with the tube. I've had that on brass before, adjusted the tickle setting, it's gone. At least on the Trotec, it was. That wasn't a leak, that was an incorrect tickle setting. Some materials are really sensitive to it, as you know, brass being one of them.
I could solve that problem in about 30 seconds without replacing the tube. I've talked a number of people through it on the phone over the years.
Lasers : Trotec Speedy 300 75W, Trotec Speedy 300 80W, Galvo Fiber Laser 20W
Printers : Mimaki UJF-6042 UV Flatbed Printer , HP Designjet L26500 61" Wide Format Latex Printer, Summa S140-T 48" Vinyl Plotter
Router : ShopBot 48" x 96" CNC Router Rotary Engravers : (2) Xenetech XOT 16 x 25 Rotary Engravers
Real name Steve but that name was taken on the forum. Used Middle name. Call me Steve or Scott, doesn't matter.