I have had mixed results with generic flyback replacements. Some work fine, but others didn't work properly. It's entirely possible it was fine at first, but then some internal insulation broke down. The only way to be sure would be to measure the output voltages (anode, focus, and screen voltages) and compare to the service manual.
Also, you said the tech cut the HV wire and spliced it. If it was a poor splice job (it's nearly impossible to properly insulate such a splice with the materials most techs have on hand) it could have arced to something and caused damage.