This REALLY helps......Common leak spots are 3rd brake light, accordian boot wire covers, sharkfin antenna and the roof rails or sunroof if you have them.
There are others for the rear but those are the only ones that would leak into the upper hatch trim.
Ensure the accordian boots are tight against the bodywork or they'll leak, and at an incline you put the hatch boot face right in the path of draining water.
I was washing the car last summer and pushed down around the sharkfin antenna and bubbles came out around the seal........wonder if that could be one part of the issue
I'll check the accordian covers.....I checked the ones to the body, but not to the hatch.....I'll do that on my next break.