It is difficult without seeing it. I take it your mobile home is like the extra large caravans. Two points caused leaks on my touring caravan. A leak seeping under the lip of the fanlight frame and another under the joint strip, I patched them but they soon leaked again. But after re-bedding both they are now leak free. Alternative get in touch with the makers explain where the leak is an they may advise better.
rob
October 2006