I had an old C8.5 project called Groove Agent Only, set up with one track of Groove agent’s Blues Rock 01. Four bars of a MIDI groove dragged onto the project. Using provided drum map.
From a fresh opening of this project I opened the full Key Editor. No red bars showing Velocity. Opened the same track in Key Editor - velocity bars visible.
Reloaded the drum map, no bars
Clicked on a drum diamond - viola all the velocity for all the track is restored.