Shower Tile is almost Level!!!

So I had to remove a bathtub and build a shower for a tenant in a fast turnover. I had my eyes on the guys doing this as they worked and it seemed they were doing it all by the book. Cement board, redguard, Liner, dry pack/weep pebbles etc.. I have seen wet spots over night on the shower floor and the pitch is just 3/8″ over 40″. It does drain, when the shower is running, but the last bit dies on the floor and is there in the morning.

I I may have a week over Christmas to redo for real but for right now I would like to do something , so an elderly man isn’t stepping into puddles. I have four days this weekend. I have suggestions to chip out the Tile which are river rock (small stones). Also to tile over the existing which seems like the safest thing, I would have to pad up one end about .5″ which is pushing it for the thinset. Any thoughts or suggestions.