I have Uforce 800 2020 as well... There is a hesitation that I would say is dangerous.  Small application of throttle seems to go from nothing to everything very quickly.  In reverse it can be scary when you are trying to creep.

My first thought was maybe the throttle was over sensitive and needed an adjustment or even a clutch engagement problem.  Honestly, when I first experienced this my left foot was looking for a clutch petal to control this better.  CVTs are great, but to me a manual would give me more control of the mesh point.

Is this what people had experienced before they replaced the ECU?  Or is the ECU addressing an engine stall or bogging condition?