I have had three quality CRTs ruined by gremlins over the years.
The first two : Zenith 1967 color 25GP22 arced and sheared neck off at CRT bell, under the yoke. RCA 1965 color CTC16X had rebuilt channel master 21FJP22 and worked great, one day I turned on and heard crackles. Necked the same way, with weight of yoke/converge yoke landing on chroma board.
The last was a few years ago, a 1965 metal Zenith 24MC32 with a 21FB RCA HiLite, the neck sheared right at the blue lateral magnet, testing like new just weeks before.
I was so upset, I gave the set to another VK member, who had a NIB crt for it.
lesson learned: NEVER spin anything metal on the CRT neck, like the blue lateral magnet/spring. acting just like a glass cutter, this may have been done before I got it when it was set up.