I have a Samsung phone also and after a while, especially when switching back and forth on accounts, it starts to freeze like you say. When this happens, you need to kill and restart JWA. This stops the freezing while darting for me.
Some days when out doing the event dino’s, I’ll dart, switch accounts, dart. Then I go to the next one, dart, switch back and dart. I just keep repeating till I get all the allowed event dinos. Doing this a lot makes the darting start to freeze, so after a switch, I’ll kill and restart the game which fixes it.
Today I did the event dino’s different. I got all on one account first before switching accounts and getting all the 9 tries on the other. I was out on my trike riding around, about 10 miles.