So you changed the network from wifi to cellular data and the game doesn't reconnect? Can you log into the game if you are start the application under cellular data?

That is correct to the first question. To the second question, yes if I restart my game under cellular data, it will work again. However, the stage is lost.

Even if you close the game, as long as you log back in within 15 minutes, you can reconnect to the previous battle normally, and you won't lose the stage. However, the network switching issue you mentioned needs to be checked, as it does not occur on my own phone due to differences in devices. Therefore, this is a more difficult issue to diagnose and will take some time.

Unfortunately, that stage did not allow me to continue it when I got reconnected within the 15 minute window. So the stage had to restart. I appreciate you guys looking into this.

Sorry, not 15, it's 10 minutes.
If you find any battle except test battle isn't recover with 10 minute. Can you record a screen to reproduce this issue. I will check this problem

Here’s another video. The beginning shows my unit attacking and then the Internet connection switching away from Wi-Fi and freezes game play.