[Master Shake]

I think that globals that leave from casters dying stop taking effect, but somewhere in the code they are skipped over and remain in the global slot. It seems like you have to overcome the globals that have been cast by dead people, but I haven't tested it extensively.

That may be possible, but probably not only for casters dying. I recast GoH using a large amount of extra gems, and it went into effect. It did not replace any of the existing globals. So it seems it had to replace a global, but not an existing one, which makes your theory of replacing a "gone" global reasonable. However, none of the past globals that are now gone went away because of caster dying - instead they were dispeled.