these KDS monitors were bad for this very same thing.

I had this exact one that did weird stuff like this, and eventually sometimes would power on with lines only.

But sometimes it worked great. I recapped it and checked all the voltages of the DC-DC circuit inside the mainboard and it was fine. still had the same problem.

So i checked out the inverter, i replaced the inverter and never had a problem again.

Strange, but true. inverter failure.