Boot style
Although I'm still a rookie when it comes to fly fishing I would take a second look at your boot stlye versus the terain. I am 64 and take smaller steps when the situation calls for better balance wether fishing a stream or hunting.
A wading staff is a must and you have taken care of that. Your pace is important as well as looking ahead for safer walking.
Get a different stlye boot for better traction and fit, our ears, nose and feet keep growing while everything else mostly shrinks.
Just and old geezer
Excuse my spelling and grammar, I hooked Mondays and Fridays to either fish or hunt.