Drivo with Workouts

I have an Elite Drivo i am using Garmin ANT+ dongle , and in trainer options i use the FE-C
Using also Garmin Cadence sensor with it.
I noticed something which affects my training actually it ruins it , I am using this program right now “4W FTP booster” And i turn off ERG mode when i start work out following the program i notice that when a hill start to kick the trainer start to increase resistance for awhile before it is back again to normal and also in Downhills the opposite happens ! while this should be a different mode and the Road doesn’t affect resistance while i am on training program “i think it is called Level mode maybe”
This issue affecting me in Sprints a lot ,any explanation ?