Incorrect accidentals on cross-staff notes in polytonal scores
S4 - Minor
1) Create a new score on a grand staff
2) Ctrl/cmd-drag a key signature onto one of the staves
3) Add two eighth notes to a staff, and ctrl/cmd-shift-up/down the second note to the other staff
4) Play the two notes, and hear that they're in the same key, despite one having been moved to a staff with a different key signature. It's easy to see when you change the staves to use the same clef, and move both notes to a degree where the staves' accidentals differ.
Workaround: You can manually change all the notes to their correct values, and make the added accidentals invisible, but this gets extremely tedious for longer scores.
See #54366: Cross-staff notes ignore accidentals