I play all shoe games and one thing iv noticed thats worth noting, is that over time as cards get played through the course of the day the stack gets thicker, so what apears to be filling exactly half of the discard tray may be less than half of all the cards in actuality. this is very noticable and has the biggest effect at the end of the shoe for instance sometimes when only six decks have been dealt it apears that 7 decks are in the discard tray and errors coudl be made easily.
-Always note where the cut card was placed before you start playing the shoe., its better to jusdge this as the cut card is inserted as guessing once the cards are in the shoe is much harder. Doing this will let you know that if there apears to be one deck left to deal by the space left in the discard tray you will know its really ~two deacks because you saw him cut off two.
Im guessing it happens because the cards get slightly bent and dont stack perfectly flush, or the edges get frayed and slightly thicker. either way it does happen and is something i havnt read about in books.
Ferret