You are posting
in the forum tech support section. This section is read mostly by the web site staff. Probably you want to ask in Construction, Maintenance
The standard way to find leaks
is to seal up all vents and use a leaf blower to put the cabin
under a small air pressure. Then go around the cabin
top with a bottle of soapy water
and spray it all over. Where air leaks out will create visible bubbles. Anywhere air can get out means water can also get in. The same trick is used by tire repair shops to find slow leaks in car tires.