MIDI velocity doesn't return to default after a single note dynamic

After applying an sfz (for example), the absolute MIDI velocity (as measured in a MIDI editor) doesn't return to the default dynamic level. In the attached example:

First note (no dynamic): MV = 80
Second note (sfz dynamic): MV = 112
Third/Fourth notes (no dynamic): MV = 96.

Expected result: After a single note dynamic the (absolute) MIDI velocity should automatically return to the level indicated by the default dynamic for that part of the score.