You mean vertical collapse (vertical deflection failure) like on this TV?
Fire is unlikely, I've never heard of any fire caused by vertical collapse. But I suppose it is possible if the loose electrical joint causing the problem experiences a lot of arcing and there are enough combustibles around. A lot of later-model CRT TVs will cut off the picture completely when vertical collapse occurs so as to avoid burn-in, but then that makes it a bit harder to diagnose the problem with the TV. It's also not a Toshiba-specific problem, it can happen with any CRT and is a rather common problem.
By the way, this post would be better suited for the "Direct View (single tube) CRT Displays" category rather than this one.