If you cannot re create the leak problem inspect the interior of the door for stains or rust.
Patio door leaking at bottom.
Spray the door and look for the leak location.
If you have a problem with water leaking it will usually be on the bottom track threshold of the non stationary door.
Sometimes water intrusion is severe staining carpets and causing dryrot at the subfloor baseboards and sometimes even the wall.
Water leakage is a common problem with sliding door thresholds.
Test the door for the location of the leak.
I plan to seal.
Aim a garden water hose with a sprayer set on mist or low at the outside of the sliding door.
6 rain hitting threshold and running down door face is splashing seeping under door on top of the threshold.
Whether your door is sagging or bowed or just not making proper contact with the weatherstrip to seal out air and water the upper corners of your frame could be the problem.
Moisture could be seeping into your home from the top.
1 place the end of a strip of adhesive backed aluminum tape on one of the side jambs in.
To slide the heavy doors along the metal frames the doors use metal or plastic rollers.
The gutters are clear and the patio is level.
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When a door leaks the most common suspect is the bottom corner of the unit.
Check to see which door moves and which one is the stationary.
Solution is a tight bottom sweep doorseal and a rain splashguard or dripcap on the bottom outer face of door like the following link the type i use unless a fancy appearing one is desired easy to diy on most doors.