Your browser should automatically update to the latest version, but if it doesn’t then you can nudge it from your GreaseMonkey/TamperMonkey UserScripts list, or else you can reinstall it from the site.

v0.41 makes the following change:

• MegaMegaMonitor icons no longer “disappear” when scrolling with NeverEndingReddit or when posting a new comment (or rather, they disappear but they come back again, now!).