2008 F350 brakes lock-up!

[JimConnell]

Help,
This only happens when I am in Corpus Christi, TX.
I drive in about 6-12 inches of sand to get to the fishing spots.
So, I think it might be the sand.
This does not happen anywhere else I drive in the U.S.A.
Last year the right front brake locked-up was smoking and red hot!.
Once I let it cool down I had no problem.
This year the right rear locked-up, was smoking and red hot and made the rear of the vehicle wobble from side to side when driving over 50 miles/hour.
Once I let the right rear rim cool I drove about 500 yards the right front brake locked-up was smoking and red hot!
Once it cooled it was fine.
When taken to the shop no one can find any problems.
Any help would be appreciated,
Jim