Steve67:
We had same problem but was
windows.
Prior to us they had re-bedded the
windows at that time they used longer screws to connect inside band to outer window frame. The originals were 3/8" #8 Robertson screws they went into a track. The longer screws went in and through back into wall area space between widow parts. This caused leak back into trailer. We filled end of holes that went to far, squished in the track, new bedding tape, new 3/8" #8 screws and no leaks.
Days of rain has tested the 4 done so far. Worst window was front one. Added new seals to all
windows only one seal not found.
So far do not think we have belly area leak but would not be supprised.
Correction on band screws they were #6 not #8 as written prior