Do you know where the water is getting in at? I see that it’s coming *out* from the grout. If I understand the situation correctly, all that re-sealing that hole on the outside will do is make it so that the water sits inside the framing. I wouldn’t plug up the outlet hole until you’ve made sure that no more water will get in there.

This for sure. I’d be worried about what’s going on under there. It doesn’t look like much caulking was used around the shower floor pan.