I'm not certain how they connect the canvas to the wall in a Surveyor hybrid. Maybe one of the members with a Surveyor can chime in.
Your thoughts about the inner seal being a possible culprit is a good one. These bunk seals do wear out over time and need to be replaced and yours are eight to nine years old.
I think your next step is to diagnose exactly where that leak is coming from and why. Water has a tendency to travel so is it the seal, the poor caulking, or something else and this is where it's showing? A bit of time spent now narrowing it down will save you time in the long run.
DW, 3 Kids and our Goldens
2012 Shamrock 233S
2008 Toyota Sequoia 5.7L 4WD