Baldwin Rebadge of Original Proteus

Hi from Washington DC. Sometime back I picked up an old Baldwin MIDI module which actually turned out to be the guts of the original E-Mu Proteus, only in a different case (and still impossible to open).
The trouble I am experiencing is that its MIDI response is horrid. It cannot respond to rapid incoming notes, like the trill of a marimba. Too bad, because a full 25+ years later I still love the sound of the Proteus.
What should I be looking for internally? Or is this just a badly made device from the start?

Thanks for your input. This is my first post in this Forum.