The either the laser tube is failing after pretty much its expected lifetime or the HV power supply is failing because that’s apparently what they do. In this case, I’d bet on a tube failure.
Although the focus may seem fine, the beam may no longer be a round spot. To check this, measure the beam shape at the entry to the first mirror; the discussion in this thread gives some details:
If the beam shape looks good, then suspicion falls on the power supply.
Power supplies tend to be cheaper and easier to replace than the tube, so that may be a reasonable starting point. Bonus: if the new supply doesn’t solve the problem, you know what’s next and you have a spare supply on the shelf.