I was exploring, and decided to battle a monster. This is what happened:

You use Rush
Your opponent uses countermove!
You were hit for 19 damage!
Turn №2
You use Blow
Your opponent uses countermove!
You were hit for 22 damage!
Turn №3
You use Blow
Your opponent uses countermove!
You were hit for 19 damage!
Turn №4
You use Rush
Your opponent uses countermove!
You were hit for 26 damage!
You lost!

Really bad luck? Or a bug?

The happens to me quite often as well. I believe it is just bad luck.

It's just bad luck, not a bug. If to consider that we have only 3 maneveurs, this situation is quite real.