Still having this same issue in December of 2021. I bought Microsoft Flight Simulator 2020 about 15 days ago and downloaded and it installed it and it seems like a great flight simulator... except when trying to taxi, my brakes are stuck at what appears to be about 50% pressure after I engage them, and there's nothing I can do to get them to go back to 0%.
Then there was an update, and I got my hopes up. After the update, which took eons to download despite having 100 Mbit internet, I found the problem was persistent.
I guess I have to try to get a refund at this point if they still haven't fixed the problem.