Try to save but say measure error
Incomplete measure: Full score, measure 109, staff 26. Found: 0/1. Expected: 4/4.
Incomplete measure: Full score, measure 109, staff 29. Found: 0/1. Expected: 4/4.
Incomplete measure: Full score, measure 109, staff 31. Found: 0/1. Expected: 4/4.
Incomplete measure: Full score, measure 109, staff 32. Found: 0/1. Expected: 4/4.
Incomplete measure: Part score: Percussion 1, measure 109, staff 1. Found: 0/1. Expected: 4/4.
Incomplete measure: Part score: Congas, measure 109, staff 1. Found: 0/1. Expected: 4/4.
Incomplete measure: Part score: Tambourine, measure 109, staff 1. Found: 0/1. Expected: 4/4.
Comments
First off, save anyway!!!
Then, be aware that "measure 109" does not particularly refer to the measure numbers in the score (if you have them). It can but it can not too. Instead, look at the bottom left corner of the MuS window.
Inspect measure 109. If you see something obvious wrong, correct it.
Can't be sure, of course, without seeing the score, but I suspect that you will see a small minus sign ("-") over the right-hand end of the four staves mentioned and (I suspect) nothing else. If that's the case, right-click on the measure and correct the "Actual Duration" to 4/4.
If these possibilities don't resolve the issue, attach the score to this forum post and (hopefully!!!) someone can take a look at it and help you find the issue.
See https://musescore.org/en/node/335842