Hi, please check that the compute method of the DataField is called once per second, according to documentation, also when the varia radar is reporting cars behind. In such case the screen is updated more than once per second and it seems that the datafield compute method is called jointly.If a datafield trust on the fact that compute method is called once per seconds errors or bad data may occur.
I have verified also that the standard slope datafield seems to go wrong when cars is incoming, when my edge 1000 display the fast moving small balls on the right, the slope goes from 0.5 % to 2% or more in a few of seconds. ( I have verified on edge 1000, last fw)