Weak laser power / 50W tube + MYJG50W power unit

Hi,
My laser dropped powers in the middle of the cutting program. It was cutting nicely with 30% power thru 3 mm thick wood, but middle of the program the path became uncontinuous and weak. First I replaced new tube, Cloudray 50W, and it helped a bit. The path is continuous, but still there's no "boost" in the laser beam after focusing lens. Today I changed new lens, but the result is same, weak.

Earlier the cutter fired vector graving nicely with 0,1% power, but now the result is about the same with 10% power. So it seems with quick ratio, that power is 100 times less than earlier. I have tested the MYJG50W power unit test button, and according to my knowledge, it works ok, thus red light emits when test button is pressed. STILL, I'am wondering, could the power unit be the faulty for weak cutting power?

Thank You all BeforeHands!

Did you check your mirrors and lens for dirt

Yes, the optical path is ok and just assembled new lens. No dirt on surface.

Today I checked the output voltage with voltage meter (or local electrician did) and the output reached only app. 5 000 vDc. It was also noticed, that the output remained almost constant, even if the percentage was tuned; 10-20-...90%. Output should be 22 000 vDc with this power supply, so the conclusion was, that the power supply is somehow damaged. New power supply is now ordered and I hope it helps.