No idea. I would suggest contacting Winnebago OR before your warranty runs out and ask them what to do. They may send you to another area dealer or instruct the dealer that's tried twice how to fix it, or ask them why it's still leaking.
That way, if this becomes a major headache down the road, and it sounds like it's headed that way, you'll have a benchmark inside the warranty period, where you reported the problem to Winnebago corporate Owner Resources, and asked them what to do, and a paper trail to support any damage or repair claims, going forward.
This is the reason why we didn't upgrade from our 2018 to the newer VS30 chassis and Navion, because the cab over bunk was not optional. When we ordered our 2018 we deleted the cab over. They are the most common water intrusion location on almost all class C motorhomes.
2018 (2017 Sprinter Cab Chassis) Navion24V + 2016 JKU (sold @ ????)
2016 Sunstar 26HE, V10, 3V, 6 Speed (sold @ 4600 miles)
2002 Roadtrek C190P (sold @ 315,000kms)