Errors in import of piano part

I've just started using MuseScore (for the purpose of modifying some instrument parts into others). My first attempt involves importing the piano part of a big band arrangement and modifying that into a bass trombone part.

The import works and is mostly correct, but it has the following oddities:
1. At several points a clef sign has been inserted in the staff. Once is at the end of a meaure, replacing the vertical line that terminates the measure -- especially strange because it is a tenor clef (!) sign that's inserted. A couple of times are at the ends of measures (correct clef signs, but in an odd place).
2. The treble clef key signature is missing on the first line (but appears at the end of the line after a double bar!).
3. The notes in the first two bass clef measures are just wrong -- but appear to be taken from some of the pitches in those measures and transcribed from eighths to quarters.
4. A "pedal" indication below the staff is changed to a "p" (piano) indication.
5. All of the cord notations above the staff lines have disappeared, sometimes replaced by indications of dynamics.
6. The last couple of lines (both staves) are simply wrong in various respects (wrong pitches, wrong rhythms).

I'm just curious about what reasonable expectations are here and if anything could be done to eliminate some of these import errors. The copy being imported is quite "clean". But it is a "big band" arrangement, and so pretty dense in terms of notation. It doesn't seem unreasonable to get portions of the treble clef part wrong, but the bass clef part is pretty much just a single bass line, and so getting the note values wrong on that seems surprising.

I'm not really complaining ... I just want to be sure I'm not missing something that would make the import more accurate/complete.