Destruction of users via keyboard shortcuts occasionally fails

Question

As folks might be aware — we've been destroying spammers at scale on Super User - which I moderate. I use keyboard shortcuts, and occasionally at some point in the key combinations I use, the site doesn't pick up, and I need to start again. Honestly, it's rare but I hit it every 2–3 days at the scale we process spammers.

While it's uncommon — maybe 1 in 40–50 times (maybe even rarer?), when I'm using mm4a to delete the spammer, one of the keys can fail to pick up. This is more obvious when it's after the first key. It works fine when I repeat the keyboard combination.

I think I finally managed to catch the error on the browser console:

Error in browser console. Uncaught ReferenceError: KEY_CODE is not defined. ...

Things I've ruled out

• I'm typing too fast. While when I use a keyboard I do have this as muscle memory, I have the same issue when I intentionally slow down. I'm reasonably sure I'm not missing keys when this happens

• Keyboard or key failure. I switched using a macro keyboard, so after the first press, all keys are pressed consistently, and at the same time separation. The macro keyboard does this at a hardware level, so we can rule out its software on my end.

• Session/JS is different — I sometimes have specific attempts at deletions fail when I've got spammers lined up and processed.

It's a weird little bug that's occasionally had me debating my sanity. I wonder if extermination would be possible?

• sjb: As this is "your site" - perhaps you might want to share what modifications you have made to the vanilla codebase. Otherwise, I suggest this might be unreproducible for others.
• Journeyman Geek: No changes - and by 'my' site, I mean the site I moderate. I've edited to reflect that. That said, that it is hard to reproduce, and its a unusual moderation workflow makes it hard to reproduce