[wa2ise]

Many TVs use a luma delay line to compensate for the time delay involved with chroma demodulation. This delay line is usually a long pipe shaped coil wrapped with foil, and then insulation. If the far end of this delay line isn't terminated with a correct load resistance, the luma signal can bounce back and forth, producing ringing like what you are seeing. Or produce the mismatch of color vs luma edges on the color bar pattern. They may instead use a "source termination" resistance, or just depend on the output impedance of a cathode follower tube to provide this source termination. The source termination will absorb all of the reflection, and thus not allow it to bounce back to the destination. Maybe a weak tube may not produce the correct impedance to make this happen. Or a drifted resistor.

To be sure it's not a misaligned IF, you could try injecting baseband video where the video detector detects the video off the IF strip. Though TV sets tend to produce a higher voltage amplitude video than that you get from a baseband video generator, so the injected baseband video will look to be low contrast.

Something else to consider: Back in the analog NTSC broadcast era which ended last year, TV station transmitter modulators (exciters) had what was known as "group delay pre-distortion" circuits, to allow for simpler consumer TV set IF circuits. Most consumer TV modulators don't bother with this, and you'd get some ringing, but the one in the Channel Master HDTV converter box CM7000 does do this predistortion. If you have or can buy or borrow that converter box, see if your TV set still has ringing.