Water puddles, Where carpet is wet up to or near a slide or wall, that might be where it's coming down and into the trailer. It could be running inside a wall until it gets to the floor. I would pull up carpet edges near those areas and look. Get on the roof and see if there are any places that puddle water, cracks around vents, marker lights, splits in the sealant. Check out the slide seals.
2013 24RKSWE (27ft TT) Cougar 1/2 ton series
2013 Ford F350 4x4 CC 6.7 engine, 8 ft bed 3.55 rear end lariat package
Retired from Oregon State Police in 2011 than worked another 9.5 years as a small town traffic cop:
As of 05-2020, I am all done with 39 years total police work. No more uniforms for me.