Player Two entering split screen as player one

I was using the beta program for the update aquatic, so when I received the official Phase 1 update yesterday, I began playing in the Phase 2 beta (with turtles); We played split screen with no issues in the phase 1 beta, but when player two entered the game in the phase 2 beta, they entered as a duplicate of player one. They still had player two's skin, but all inventory items and armor were exact copies of player one, meaning all items that player two had been holding when they left the previous game were lost.

Player two left and re-entered the game a few times, but with the same result. Also during this time, both players appeared as white markers on the map, but the marker flashed back and forth between player one's location and player two's location (there were never two markers on the map at the same time). Finally, after we played this way for 5-10 minutes, the game froze (player one was mining, player two was swimming, in case that matters).