[Hildryn Prime: Hotfix 32.3.6]

Remapped keys are reset mid-mission in 80% of missions. They are reset to default values, even if the new key was not just added as a duplicate, but it replaced the default one, and the default one was generally removed from the list of keys. Specifically, in my case, I COMPLETELY replace the heavy.
melee weapon attack from "Mouse Button 3" to "Mouse Button 5" (aka side button or "Forward"), that is, I exclude "Mouse Button 3" from the list of buttons for a heavy attack. And yet, during the mission, the reassigned button ceases to perform its function, but the excluded default one starts working.