I have a Mi Pad 4 Clover wifi version and also have the same problem. Actually, I've noticed this bug only on the last 3 weekly builds 9.5.16, 9.5.9, and 9.4.25. There was no problem with 9.4.18 or before. Hopefully the devs will fix this reverse nav button error. I prefer the nav buttons to the gestures as I find them faster, especially for recent apps.