Can't speak for a Scamp
but my '78 Trill leaked like a sieve from the roof vent, perimeter windows seals to the trailer and belly band.
The window leaks
are likely from the seal to the trailer and not from the mechanism of the windows, but, you may want to look at that also. The wood holding my windows in was completely rotted out so I assumed the perimeter window to trailer seal was shot which it was and verified.
I had rusty stains on the lower benches & closet floor from belly band leaks
and on the floor from the roof vent which were all verified (with window leaks) by sitting in the Trill sipping copious amounts of beer in a driving rain storm.
I suggest you buy a 12 pack and investigate one possible leak at a time in a driving rain storm to eliminate all options.
All of this is just speculation on my part for your Scamp
, but, as the Spanke Family Motto States: "We may be wrong, but, were are never in doubt"
Good luck on your investigation!