Is there a reason you are using Auto 20/40/80 setting in the first place??
In my experience, I set it to 80mhz and forget it. It worked well for me for many years with no issues. If a device is too far away from a router, then connection speed will drop do to distance, but I don't have to worry about speed step down if a device is close to a router and I don't have to worry about router choosing speed connection based on a channel.
So why are you using Auto setting in the first place?
There was a post awhile back by @Grisu where he tested the individual settings and auto and a lot of them weren’t actually doing what they were set for. Auto 20/40/80 was actually working correct vs the others. Maybe he can clarify that since I can’t find that thread now