I pulled everything apart on the inside of the slide and with a flashlight and remote camera inspected everything I could get to. There is zero evidence of water coming from any of the lines and no water intrusion into the inside of the slide.
Then I went outside and started inspecting every inch of every seal. I discovered two places where the seals were not firmly attached and when running the slide in and out it was obvious that water would be channeled into this area when driving in very wet conditions. Additionally, just sitting in heavy rain would give water an opportunity to get in if the wind was right.
When the slide is all the way in the bulb seals are touching but not with any significant force, certainly not enough to prevent intrusion under pressure. I used some clear sealant to try and clean up the way these seals are attached.