Tile Failures and Problems

here is the long and the short of it. Built a wet room in my second story bedroom/ bathroom and replaced the subfloor with new wood and plumbed in the shower drain and free-standing tub. We ran new copper pipes and installed all new drains, then called in a hot mopper who came in and hot-mopped the 6x6 area. he went 10" up the wall and did what i beleive was a good job short of getting tar in the weep holes. We did a drain test and it held water so we assumed it was a clearance to go forward. Next we called in a tile installer to do the shower pan, i havent done one before so figured it would make sense to call in an expert or so i thought. He installed the drypack with 1.5" on the far side of the walls and sloped a bit more then 1/4" to the main shower drain. At the shower drain itself the pack is only about 3/4'' of an inch thick not sure if this is an issue or not. Myself and a friend installed the shower walls using 3x4 large white tiles, the walls were done with hardie backer and we did 2 coats of redguard first prior to tile. After the walls were done we waited a week and started our floor. WE used a matte black 12x12 mosaic sheet started at the far walls then worked our way to the drain which isnt in the cent but closer to the door. Finished the tile then used Mapei grout and grouted the floors. After about a month we noticed a leak in the downstairs bathroom ceiling so we took the drywall off and exposed the plumbing above. the drain arnt leaking but what we have discovered is that the shower after running for a long shower say 30 minutes starts to build up water between the drypak and the hot mop. This amount of water is a pretty good amount because the water goes away from the drain up the slope and finds an exit through a spot in the far end of the shower. WE have taken out the drain and redone the drain cleaned the weep holes and added a nice amount of gravel. How is it possible that water is getting in between the drypak and the hot mop and building up so much water that it goes up hill and exits? Ive searched for cracks in the grout and tile and there is none, ive taken 100% waterproof calking and gone around the entire shower between upper tile and lower. i really dont know what to do and i dont want to rip up all this tile. Can i just put an epoxy over the floor to waterproof the entire floor? its been 2 months with no shower so i really need a solution quick, ive even considered getting a piece of granite to go over the tile floor so it 1 piece but i assume the slope becomes the issue here. Any advise would be great.