Common problem with winnebago. Depending on braking system it could be a cheap fix or cost you thousands. Had the same problem on my 2008 winnebago, the braking system they use will show a ABS light problem and it's the entire hydraulic brake system.
Cost for our part. $6,000.00. I thought the braking was normal also, but the Winnebago tech informed me I was only operating on front brakes. He said after a short period it would go to no brakes.
The tech told me he sees the problem after long periods of sitting or a bunch ofr dead battery starts which destroy the unit. The brake system needs to be exercised.
Get it to Workhorse immediately. Don't play with your braking system.