I'm very happy to say that everything appears to be working correctly now! Though I'm not sure why it's suddenly working after consistently failing for hours just one day prior. I didn't so much as look at it, much less tweak anything. My best guess is that Chrome might have been using a cached version of the web UI files that was somehow only slightly incompatible with the version of the web server that the Duet 2 Wifi was running? I really don't know. Sorry to waste your time! I was able to use the web UI to fully configure all endstops, motors, run M303 for all three heater elements, and reset the board multiple times while configuring, all without so much as a hiccup, so I'm fairly confident that the issue is gone. However, if it does rear its ugly head again, I'll make a new post within this thread and include the results of the M122 then.
Thanks for your time!