Fix the leaks before they start with careful framing and the proper sill pan, flashing, and sealant.
French doors have a reputation as being leak-prone, but most problems stem from improper installation. Here, a spray-rack test shows water leaking between the sill and the subfloor.
Both one-piece metal door pans and multipiece plastic door pans should be fully bedded in a high-quality polyurethane sealant, not silicone caulk.
Membrane pans should always be used with compatible flexible corners and sealants from the same manufacturer; many plasticized sealants are incompatible with peel-and-stick flashings.
A pair of compatible flexible corner flashings set in beads of sealant are used in conjunction with 12-inch-wide peel-and-stick flashing.