This is a KoLmafia bug. It's a race condition. I'll discuss the specific issue in the bug report thread you opened.
I learned something about Guide when I was looking at Bale's choice.php/shore.shop.php relay script override issue. He runs Guide, and the debug log he submitted showed me that the browser was repeatedly asking for relay_Guide.ash. The browser - not the user. Apparently, just like chat, that frame instructs the browser to periodically submit a URL; chat polls to see if there are new messages, Guide looks at the current state of your character and decides what to recommend for you. In Bale's log, KoLmafia was in the middle of executing his choice.php override when the browser submitted a request and we went off to execute Guide, before returning to finish up the choice override script.
Very clever. I don't actually understand the mechanism, but, near as I can tell, this is the first relay script that does that. In any case, it means that periodically KoLmafia runs an ASH script asynchronously - in its own thread, in response to a browser request - while other things in the Relay Browser and/or the gCLI and/or the GUI are doing things. In this case, the bang potion identification code is updating and sorting a data structure that Guide is also examining. I'm amazed that we haven't seen other things of this ilk coming from this script before.
But, as I said, it's not a bug in Guide.