Bug: Updates in the primary tree only unsuspend once

[gaearon]

https://codesandbox.io/s/upbeat-frost-3tt25

1. Press Suspend, see "Loading..."
2. Wait five seconds, you'll see "Happy birthday" at some point
3. You won't see it again no matter how long you wait

Expected: you'll see it every five seconds.

[gaearon]

Here's a variation that doesn't seem to "wake up" at all, not even the first time: https://codesandbox.io/s/sleepy-moore-4e3o9.

[acdlite]

Confirmed that this is fixed by #18384