help brake problem

[soccerloco]

have a 2012 forest river lx3112 toy hauler and all of a sudden I have a brake issue.

Adjusted brakes first and checked brake controller all seems ok. When I apply brake controller or brake there is a humming noise in the brakes but not braking.

If I remove safety brake tether the brakes lock up immediately.

Not sure how to proceed any help would be greatly appreciated.

Thanks

Bill