So, guys, I was battling through Ryi's 5th stage on the third pass and during the first battle encountered 3 or 4 (don't remember exactly) times in a row an increased attack of 52k, while his girl must deal 35k. The second battle I decided to give it a closer look. The situation repeated, a couple of her attacks were as if she was lucky and her ability dealt 50% additional damage. But there were no indication of it AND it worked ONLY when my girls used their own ability AND it happened way more than her 9% intended ability chance.
That was weird so I decided to make a video for proofs. Here you go - video of 3-14 battles with Rui on the 5th stage. You may see this shit happen multiple times.
Today I'm battling Ryi's first stage and everything seems normal, so, I guess, it's some bug on the fifth stage only.