How to Recover from Failed Patching

I have a bad feeling I already know the answer to this, but I'll ask it anyway - how do you recover from a failed patch?

The error I get, briefly, is:

[0.616250] Initramfs unpacking failed: ZSTD-compressed data is corrupt

And then when it gets to the boot sequence, it hangs at:

[OK] Started gdm.service - GNOME Display Manager....(other stuff)

There are no other visible errors here. Attempting to boot a kernel backup just results in the same hang. Going into rescue mode shows a number of other errors in the system log, but there's far too much in there for me to make heads or tails of.