Common Problem.....new to me

[sailorii]

Have a 2009 28' Flying Cloud that I purchased new in 2010 as a model year left over. Have had great service so far. When I purchased, noticed a small stain on vinyl floor just forward of the door against the wall. Feeling dumb today-just discovered a small(6"x8") soft spot in the underlayment in this area-evidently have had a leak all along. No signs of leaks in the interior ceiling....water tracks, etc.
Looking for advice on how to diagnose source.
Although everything looks good, TV antenna could be the problem. Do I remove the antenna entirely to recaulk? I suppose it could be the radio antenna. Maybe the door frame although the spot is slightly forward of that. Can water get in to the sub floor at the molding at the bottom of the aluminum exterior wall? If so, what is the solution there? Has the wrap around windows; but, they are a little forward of the spot.
Just looking for some thoughts on how to proceed. Thanks.

[arktos55343]

Water can travel and show up in the oddest places. However, I would suspect the window forward of the door. Water can indeed leak into the top of the rub rail molding (and any seam...anywhere), so it is important to seal the top edge of it all the way around. Could also be a leaking roof vent. Do you have name plates forward of the door? They could also have a failed rivet, allowing water to infiltrate.

[sailorii]

Thanks, arktos5543. Will admit, I haven't done a close inspection of the window. Would have never have thought of the nameplate.