RCA 27V530T Having problems (by 2 users)

To me, it sounds like a bad solder joint in the flyback area or the vertical output section. When it is operating correctly, can you induce the failure by whacking the top or side? That is not a "definitive" test, but can indicate a bad wiring or solder connection.

You can inspect all joints and connections looking for a bad one, but it often takes a trained eye to really know what one looks like. Sometimes they are very obvious with a distinctive crack around the solder connection. Other times, the bad connection is inside the joint and not visible to the naked eye.

If you are handy with a hot iron, you might be able to find & fix this yourself.

Right now, your TV is telling you it needs service. Take it in and have it repaired before some major part blows due to surging and arcing across/through a bad joint.