Shower leak in floor below have caulked could it be the door tracks that sit on the shower pan

It could be any number of places. It helps to know how direct the leak is below, if it is dribbling off to one side or not. Where tiles and pan meet on floor, holes drilled in fiberglas pan, but also around the drain or the water supply at the faucet or shower head, down inside the wall. If you can cut out a square of ceiling below?

AS JP said above, it could be anything really, huh?

I guess here, the first thing I would do is to take a 5 gallon bucket of water and I would pour it down the drain 3 or 4 times (15-20 gallons) and I would see if the drip showed up downstairs. Be sure to give the leak time to show up, OK? If so, the leak is isolated to the drain or the shower pan.

If that didn't result in showing the leak then I would remove the trim plate from around the shower valve and then run the water to see if anything is leaking behind the wall.

If either one of these tests do not make the leak show up then I can think of a couple more tests, but try these first... see what happens and let us know, OK?

Finally, what condition is the tile wall and tile/grout in? If there is any cracked or missing grout I would suspect this may be the issue in itself!

Back to you...

Mark