Fix errors in an import and additional questions.

I'm a hobbyist and have only used Musescore previously to convert PDFs so I'm not an experienced user. I'm now trying to use the program for more things, but I've run into a situation with a .XML export from Reaper 7. When imported into Musescore 4.3, the file gives a message that it is corrupted, but it still can be imported. Most obvious was the sustain pedal info came in misaligned, but I deleted those as they are not necessary for this. However, I noticed that many note lengths have also been altered. The piece is in 3/4 and many first chords in a bar have dotted half notes (3 beats)

They are not this way in the Reaper notation. The top Bb in the image should only be a half note. However, If I change it in Musescore, it changes all three notes in the chord. Should that happen?

Shouldn't I be able to edit the length of only that note? Is this a function of Musescore, or is the .xml import being corrupted in other ways? Also, when I save I get warning errors that I think are related to this. I think the incorrect note lengths are not adding up for the time signature?

The image is measure 2, and the lowers staff is staff 3 of the first error below.

e.g.
Incomplete measure: Full score, measure 2, staff 3. Found: 7/8. Expected: 3/4.
Incomplete measure: Full score, measure 3, staff 1. Found: 8/8. Expected: 3/4.
Incomplete measure: Full score, measure 3, staff 2. Found: 11/8. Expected: 3/4.
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Incomplete measure: Full score, measure 4, staff 2. Found: 4/4. Expected:
Incomplete measure: Full score, measure 30, staff 3. Found: 11/8. Expected: 3/4.
Incomplete measure: Full score, measure 31, staff 1. Found: 7/8. Expected: 3/4.
Incomplete measure: Full score, measure 31, staff 2. Found: 13/16. Expected: 3/4.