I think I have referred t this before, but we had, as part of the ENG setup on a helicopter, a very small Sony Trinitron, (around 50mm) mounted in the instrument panel.
Although it was not "flight rated" we had a "special dispensation " to use it.
As happens, eventually the tube lost emission & died.
With great difficulty, the tiny device was dismantled, a new tube fitted & adjusted for best picture.
Running on test, & with judicicious"bumps" it refused to fail, so it was refitted to the "chopper".
Sadly, it failed on its first outing, so back it came so we could investigate.
No faults could be found, so "just in case" several "possible spots" were "anchored" with neutral silicone sealant.
Failed again!
After a couple more iterations we apparently "hit the jackpot", as there were no more failures.
It was very unsatisfying, as we never knew which blob of sealant finally did the job!
The joke around work was that we had a "vibration desk that could fly!"