Just so you are aware, I thought I had no leaks as well until I removed the interior window them and vent trims. Water can leak in and work it's way between the laminated layers then down the side without ever seeing a drop of water. It would be an easy and prudent step to remove the vent trim during a rainstorm to check for dampness.
On my trailer, the caulking head been redone just before bought it last year, and it looked good, but everything was leaking.
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