Similar to this bug but not the same.
Whenever you start playing MIDI, and the playhead begins at the same position the MIDI does, the velocity is significantly reduced. Here is the issue in action
EDIT: It appears this might only happen when DAW Sync is on
Mac Studio Sequoia 15.3.2 | Logic 11.1.2 | Scaler3 Control 1.0.2.40304e4