hub: edits can get lost

[shikokuchuo]

You can get into a bad state where you type and then it disappears. On a collaborative session for Shiny team meetings (7 users).

Possible history with no changes? To confirm.

Switching and coming back fixes the bad state.

[shikokuchuo]

This has improved a lot, but we reproduced this. We can see in replay that very fast changes are deleting text created by another user.