Hey @bestlem apologies for the trouble you are facing. Is this something that you can reliably reproduce?
I tried following some rough steps like you mentioned, i.e. First opened 30-40 tabs in vertical tabs mode (some nested, some not nested). Then I closed tab trees and single tabs using close tree, close tab, close tabs below, etc. and only kept 2 tabs open. I was able to successfully switch between those tabs.
To get to the bottom of this bug, if possible can you please share some series of steps which cause this issue? Also, you mentioned that this happened after the mac slept - can you elaborate more on that? Did the issue start happening after you woke up your mac from sleep while Orion was open?