First note is not playing after opening a score if patch change was performed in a mixer

1) Open the attached score (from #284426: Instruments play as piano with odd side effects).
2) Open Mixer.
3) Change a patch for the Flute to Trumpet.
4) Close mixer and the score (not saving changes).
5) Open this score again.
6) Press Space to play the score.
Result: the first note of the Flute part is not playing. Other notes play correctly. After relaunching a playback the first note plays well too. Reopening the score reproduces the bug again.

This doesn't seem to happen to other scores (maybe having midi channel assigned in this score plays some role, like it did so for #284426: Instruments play as piano with odd side effects). Still changing patch in a mixer in absolutely different score leads to this bug too.

This bug is reproducible at least in MuseScore 3.0.2 (in Linux AppImage, revision: 8ca4d2c) so it doesn't seem to be caused by changes made regarding parts playback. After applying this fix for #284426: Instruments play as piano with odd side effects this issue can be reproduced again.

The workaround is, at least, replay the score again, or click on the first note before starting a playback.

Not sure about the severity, this issue is not good for playback but seems to happen in some rare cases.