Need some advice (help) with my CTC-16L

[jstout66]

I need some advice on what to look for concerning an annoying intermiitant problem. This is on the CTC-16L I got off eBay a few weeks ago. When I got the set, the picture was pretty good, but you had to adjust the controls more than usual when you turned it on. I suspected some bad tubes and found some assorted ones with shorts. What I changed (and I did check the new ones) was the 12BY7 both 6GM6's both 6GH8's 1 6HZ6 and the 6KZ8. Now every once in awhile the picture will flash green and go back to normal. I noticed the kine bias switch was a tad touchy (and would cause the set to flash if I moved it) and I cleaned it. The set still does it. I suspect from troubleshooting in the past that it may be the 12BY7 or maybe even the 6GU7's altho they test good. I was a dumbass and threw away the old tubes. The set didn't do this until I changed them. What do you think I'm looking at? I was careful with removing the tubes and all connections seem tight. I don't think the picture tube has a short, but won't rule that out. I'm mainly leaning towards the tubes I changed. What do you guys think?