Here’s a weird one: I have a bar of piano music, wherein the beats of the lower clef are correct in 4/4, but in the upper clef, an extra sixteenth and a half note is added for some reason (probably owing to something I did previously). I can make it disappear with the “Remove rests” function, but as you can see from the rhythmic grid markings, the extra sixteenth and a half note is there in the rhythm, even though it’s a 4/4 bar (as are the bars before and after it).
I want to add a sixteenth note at the end of the upper clef, but cannot do so correctly, since this extra note value is always inserted after it. It’s especially strange, since the lower clef has the correct note durations (although probably from just deleting the rest). How can I make the bar revert to the proper 4/4 rhythmic grid?
I think your file is an XML import. However, move the caret to the extra 1/32th rest. Press shift b and input | in the popover. This will create a strange short bar. Select the rest in that bar, press shift b and input -1. Done 
That did the trick. For some reason, I had to add 2 bars, one with a 16th rest and one with a 32nd rest, but I could delete them both. Thanks, Marc, you’re always a great help.