What I mean is, are you in the middle of the fight when it crashes? Right after you tap the 'Fight' Button to enter the fight? At the end of the fight?
I do not have reports from any other players with this issue so trying to get as much specific info as I can.
By chance do you play with a screen protector on? If it happens often enough, I recommend playing with 'taps' turned on and recording a video so you can verify if it's an issue with your device. To turn on 'show taps' you'll need to enable developer mode: on Samsung, you typically to the 'about phone' section of your device and then tap on the Build number 7 times. Then you should see a Developer mode option in your settings.