I downloaded the 1.13 player and attempted to make a backup of a 1.12 Minecraft save game.  Attempted to make backup of this save game, using the EDIT and MAKE BACKUP buttons.  The player hung and I was forced to crash the player to get back to my desktop.   This problem repeats, so it appears to be a genuine compatibility issue.    The backups that were created in the backups folder appear to be corrupted- Windows cannot open the zipped folders.