More issues with grace notes & pianoroll

OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 3.4.2.9788, revision: 148e43f

At measure 15, on the Alto Clarinet part, the grace notes currently look good on pianoroll but play awfully - they're way slower than they're supposed to be, and the "chief" note they refer to starts playing before even half of them have come by even though on the pianoroll it looks like they should all be done already.
This is already heavily edited on the pianoroll, since by default, while there's no such superposition, the grace notes are also pitifully slow...