This occasionally happened to me on iOS (in the example screen shots, it is on iPad Pro) -
After the other kid blasts (or farts), some units get thrown out of the battle arena. They continue moving toward the opponent and may eventually reach it, but "ideally" they should have bounced around a bit and not gone out.

See two sample cases below -
https://imgur.com/a/kJnYnkc
https://imgur.com/a/vZgD1kb
https://imgur.com/a/xY1lvp4

BTW, this forum is a nightmare to submit bugs on ; you should really support uploading photos directly...