I love your videos! They are always full of new surprises! I tried biking and the same thing that you described happened to me and my prosthetic foot kept sliding out of the pedal. Unfortunately, when I went to dismount I forgot to do it with the "meat leg" so I stumbled and landed on my right wrist, breaking the wrist ( I feel like a real fool) so I think I won't use a bike for a while. I have started a small group of amputees and a physical therapist to instruct us on the finer aspects of walking on different terrains ( I live in Maine and it's very hilly and uneven so it is a real challenge) But it's always good to hear your adventures