Hello,
Thank you for the Bug Report!
I am unsure of what exactly is happening. Since there was no replay or screenshot I’m not quite sure what is going on to cause the crash. I have tested Comic Relief and the effect did not cause the game to crash.
You can see here I have resolved the effect swapping a comic relief, via the Comic Relief scale effect, with the opponent’s monster.
I believe you may be using Windowed mode, which has been known to cause the game to crash when swapping windows or just in general. This has been documented in the #Tech_Support channel in the Duelist Unite Discord.
You can also view Case 4 on the forums here: Installation and Troubleshooting Guide
If you believe this is the cause of the crash, please feel free to mark this as the solution. If you do not, please let me know if there is something else you believe to be the cause and details on how we can test it.