I would suggest that rather than talking with the rep over the phone you actually take the unit to the factory service department in Forest City IA. In cases like yours it's almost impossible for you to describe and the rep to visualize everything that's going on in the few seconds it takes for the slide to act up.
When the factory technicians can actually witness the problem you stand a much better chance of getting it repaired properly. It may be inconvenient, but a single visit will likely cure your problems once and for all. If you do decide to go take along all the paper work from your visits to the dealer. There are cases where Winnebago will make "good will" adjustments if this has been an ongoing problem the dealer hasn't been able to resolve.