The "canAdd" scripting command (https://community.bistudio.com/wiki/canAdd) will return false if you have too much "weight", even if you set "_unit enableStamina false;" (https://community.bistudio.com/wiki/enableStamina).
Essentially, even if you disable the stamina system, the "canAdd" function is still limited by it, even though it doesn't factor into the intended gameplay at all.