You better check Anode (red wire) isolation.
Even if the laser was dead there CAN NOT BE arcs like that. NEVER
Put some plastic between anode and machine body and check again.
Dead lasers are dead. They do not makes the air more transmitting for elecricity.
As I see on the picture ther are two dark points on the plastic anode hood.
This looks to be arc sign.
Remove - very gently - this plastic and make new isolation using special self-vulcanizing rubber tape. DO NOT USE ORDINARY plastic tape.
Isolation should be thick all around anode (small metal rod coming out of glass) and red wire.
I think you propably tried to start machine just when she came and there was some wet from the air.
CNC lasers, constructions, service