Any thing is possible.
I would start by removing the bench seating and remove the wall board carefully, to see what lies beneath, by your photo's it looks like there are two possible water ingress area's, the awning rail and the window seals.
By removing the wall board you can then decide if it is worth repairing, but you must identity where the water is coming in and rectify that as well. its a long and labour intensive job but the satisfaction when completed is worth it.
word of caution the video Posted by Dusty dog shows there is a tube of gripfill, he didnt show he used it BUT it is not solvent free and you would be looking to use solvent free products or your insulation will get eaten away!!
if you do a search for Damp repair on here i posted some photos years ago. I will try and find it tonight when at home..........I'm at work skivving at the mo
