05 E-150 fly by wire. If you are cruising along and hit the brakes fairly hard the cruise will not resume. Try set won't set turn if off and back on still no set. Come to a stop and and take off.
Turn cruise on and it will set and resume. So it is somewhat intermittent. Leaning toward brake switch anybody else seen this on the fly by wire vans

 

I've had two brake pressure switches go bad on mine (with related cruise control issues).

My symptoms did not match your description though.

However this pressure switch is a common failure point so you should start there.

 

Replaced switch yesterday so far haven't been able to replicate problem.