The [iRobot Braava m6 has a threshold problem](https://homesupport.irobot.com/app/answers/detail/a_id/21012/kw/Threshold) and it is a bit frustrating but workable. In my case it can easily go from laminate (higher) to linoleum but not the other way. It’d perhaps take just a quick rev of the wheels to hop back over up to laminate.