Creating individual part sheet music doesn't retain formatting very well
One of the major conveniences of music software is that you can compose a master score, then have your software separate the parts and print out copies for each of the musicians... This feature is heavily underdeveloped in MuseScore
List of issues (there are probably more):
Line breaks should carry over in all four parts
Repeats created in the middle of the measure (due to pickup notes, etc.) are not carried through all parts.
Text labels ('Trio', 'Var. 1', etc.)above stave should carry over in all four parts.
If a grand staff is joined together with a brace, then that brace should disappear when creating parts. (Currently it appears on the first part only; the other parts have a strange missing left-side bar)
Comments
As spotted some problem remains ensemble scores but the nightly builds of MuseScore already contain some fixes.
David Bolton started a page to gather the differents tasks. See Milestones
I don't recommend using "middle of the measure" repeats they have several problems. Use two incomplete measures instead. Read about Actual duration in the handbook: measure operations .
If you want text only on one staff use Staff Text. if you want text to export to every part use System Text.
The problems with braces is a known issue. For details see http://www.musescore.org/en/node/3626
Whether line breaks should carry over to parts is questionable. I prefer that they don't since the layout of a part is completely different from the full score.