How to restore correct playback of dynamics and hairpins in an imported MIDI file

After opening a MIDI file, you may find that dynamics, and crescendo and diminuendo lines do not affect playback as expected. To fix the problem:

1. Open (import) the MIDI file;
2. Open the Inspector (F8 or "View→Inspector") if it's not already open;
3. Select any note, then right click and choose "Select→Select all similar elements";

4. In the Note section of the Inspector, locate the "Velocity Type" and "Velocity" properties (near the bottom). E.g.

5. Click on the "Reset to default" buttons for both values.

This should reset all note velocities to MuseScore's default value (i.e. "Offset" and 0), and restore correct playback of dynamics and hairpins.