Strange errors with Blackjack App

Student is trying to make a Blackjack app. Most of it is functional, however the shuffle function for some reason seems to make the completeDeck list empty, and thus does not work the second time it is used. Furthermore, attempts to use the debug break command in certain areas, as well as attempts to slow down the speed of the code being run in order to see what’s happening, will result in the program stopping and not doing anything. Any help would be appreciated, and the link is provided.