In Normal and also in Sport mode the descending speed is throttled to 10 km/h.
If you ascend and then descend, the speed in 21 km/h for a very short time and then immediatly goes to 10 km/h.
This bug is really annoying

I thought I was crazy! It like jolts downwards for a brief bit going too fast, right? It scare the crap out of me the first few times. I thought it was my stick sensitivities.