I wonder if the Tire it self has become conductive? Shango066 on YouTube talks about that a lot on these old RCA sets. And it usually happens in the exact area mine is having major issues with. Right below the hat that the HV Rectifier tube goes in too.
Here is an idea: Carefully see if you can peel the tire off the flyback in the effected area, go to Autozone, or Advance Auto and get Permatex UltraGrey RTV and cover the effected area completely with a layer or two of the RTV to see if that solves the issue it's suffering. It really sounds like the tire has become conductive internally.
Look up Shango066's videos on this. He's repaired much sicker, weaker flybacks this way and it seems to hold up. It's not pretty, but these parts are unobtanium and I cannot afford to source a new fly.
And I don't want to sit with a sick lump of a TV I'm never going to do anything with. I haven't the space to just sit and let it do nothing. I only have room for one single TV this large. If the fly in this set is sick, and you have the patients and time to source a fly, fix the CTC20 and keep the CTC16.
Keep me informed.
Vidoes:
https://www.youtube.com/watch?v=BUnPkymnxUw
https://www.youtube.com/watch?v=OHyQo76ySG4
it's not pretty but this might save the CTC16's fly.