Tricky corrugated metal roof with EPDM valley

I have a corrugated roof that flows into a valley(which is up against another building) lined with EPDM. The water then has to travel sideways 18 ft, to get off the roof.

The problem is, water is getting under the bottom of the metal and traveling back up. There is 3 ft of EPDM under the bottom section of the metal but water gets in.

This issue developed when we put the metal roof on top of a corrugated fiberglass roof that had problems in other sections. The original roof had a 30" EPDM valley with 16" of EPDM under the corrugated fiberglass roofing. The guys that put on the new roof left just a 16â€Â