Flight start, departure and cruise is all normal and fine, then seemingly all by itself randomly in the middle of the flight, the 'Brake' word in lower left corner will come on. I've check and yup, brakes psi in the plane is fully applied. When landing, plane stops very quickly and will not move once stopped on the runway.

 

Doesn't seem to matter what plane. Happened to me in a Captain Sim 727, freeware Lockheed L-xx49 Constellation and  Concorde X so far.

 

I've tried unmapped all brake keys, checked parking brake in plane and options and check unmapping for brake axis. Nothing I try unsticks the brakes. I fly pretty simple, only use mouse, keyboard and Rumblepad 2. No pedals or rudder or any fancy stuff.

 

Suggestions on what it might be?

Autobrake knob isn't set to 'RTO' is it? (Not that this would apply to most of the aircraft you listed)

I have ch pedals and sometimes get this problem too.  I find pressing control period to set parking brake, then press brakes on pedals (or press period button again) helps clear it.