Are your panels in the correct position? When using the shower make sure the inside panel is against the showerhead wall so that the overlap prevents water from getting out between the doors.

Yes.
The inside door is on the same wall as the shower head. I even tried moving it to the other wall, but it still leaks.

Sounds like your track is installed backwards. The track should evacuate into the shower.

What Treb said, there are weep holes for the water that gets into the track to drain back into shower if installed correctly. Single track or two track there had to have been a gap between the doors the track was more than likely just installed correctly on the previous unit.

I agree the track looks backwards. The soft rounded edge would face into the room I would think.

Even if the track were on backwards wouldnâÂÂt part of the problem be in the shower threshold not having a pitch toward the shower area? Sometimes these knuckle heads do a level threshold and it does not allow water runoff toward shower/drain. Get out a level and see how that threshold is pitched.

Very well would not help but if the weep holes face the wrong direct the only thing that would stop the water would be if were dam near vertical.