How can your avatar coast to a stop on a -5% grade? The physics with this game is whacked
What trainer do you have. Does it show power while coasting?
Also, descent grades are halved, so it’s really only a -2.5% grade from a physics point of view. Still hard to believe you’d coast to a stop, but easier than 5%.
IIRC Zwift halves descent grades by default then whatever your Trainer Difficulty is set to also factors in. I.e. if you are running 50% TD (default) then a -5% grade would be -5% x 50% (zwift half grade default) = -2.5% x TD% (.5) = -1.25%
Wahoo Kickr - No power output while coasting