this is just mvm being a buggy piece of shit
sometimes the mann up servers lose connection with valve's validation servers (that grant them the ability/permission to give out item drops). there are a lot of things that can cause it. when it happens, all of your tour counts on the scoreboard will either say 0 or disappear, as if you were on a boot camp/unofficial server. the only way to fix it is to relobby.
that is, assuming you don't get your items. if you get your items but the screen bugs, it's still mvm being a piece of shit, but no there's no fix and no way to tell when it'll happen. it isn't the fault of the HUD.