I don't know if this has been logged or not cause I have not been able to search for it correctly since 4.5 upgrade
These things have started showing up in my scores I get rid of them and re-do the measure and it then shows up in another place.
Then sometimes when I go into edit mode, place a note and it scrolls me to some other place many measures before that. So I guess that is two separate bugs since 4.5 upgrade. Thanks for your time. 
Comments
Here is the fix for the latest bug stated above: If you import a music xml file or midi file and musescore doesn't like a measure(s) even though it goes ahead and imports it, these red squares are the flags for the errors it found. For instance: "Incomplete measure: Full score, measure 130, staff 2. Found: 5/4. Expected: 3/4." (Btw, it does not flag the measure as 5/4 !)
I went back to the measure listed in the error and created a new measure beside it and rescored it exactly as the one that is flagged (you can't copy and paste notes from the flagged one or it picks up the bad code) then, delete the flagged measure and your score will load correctly without of course or thankfully, the red box. Dorico's crappy interface is looking better and better.
In reply to Here is the fix for the… by glovemtb77
I haven't run into the red box yet. Hard to say just what is going on without the score. Did you happen to try deleting the two half notes?
In reply to I haven't run into the red… by bobjp
Hiya thanks for replying see my second comment I think I figured it out. You can actually delete everything in the measure and it still shows red box. That made me figure out it was just confused code And my fix described above worked. You wouldn't see it unless you imported a lot of XML or MIDI files like I do. I keep trying to use Muse as my primary reader and composing software and I just keep running into bugs that never get fixed. For me the biggest one is the fact that you cannot lock the score when you're playing it and just using it for sheet reading. Then my second pia one is if you slow down the music your cursor jumps way back from where it should be. If you speed it up, it jumps way ahead. I've documented that one and how to get around it on here. If you ever run into it and want me to quickly tell how that works just reply. Thanks for your time.