Why does X sometimes break the system while exiting, and can I fix it without rebooting?

The system in question is a laptop running Gentoo. On some occasions, I'll have been playing Minecraft (modded, under the Technical launcher), and then quit game and launcher, log out of X, and get a black screen with an unblinking cursor in the upper-left coer. This is the third time it's happened; the last two, I ended up rebooting. I would really rather not, though. The usual VT-changing method (altF1, with and without control) has no visible effect for VTs 1 through 7. controlaltbackspace similarly does nothing. From experience, the magic sysreq keys work, but the ones that should print things (h, for example) don't.

Can anyone provide insight into what's going on here? Can I recover, or do I just have to reboot?

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