Axis Bomber Boy 'Mark' heals enemy instead of damaging

[podstrahuy]

I've found very frustrating bug.
Axis Bomber Boy basic attack 'Air Strike' have 30% chance to Mark enemy for 4 turns. Description of this ability says that the Marked enemies taking additional true damage on Perfect hits from your team.
But it works in opposite way - the additional true damage healing enemies instead.
I've made few examples to show just how it's annoying.

Screenshot with the enemies after Axis Bomber attack, 3 of them are marked, so they should receive more damage with next attack:


And the result of perfect attack of Carriage Rider Eddie:


They all should be dead after that attack, but they received healing according to True damage that was shown on attack (about 400). The enemy without mark is dead.

Next example. Same enemies on the sides with same class, but:


Only marked right enemy survived:


Seems like 2 worms are dead because they received more damage than they have left + true damage healing. Eddie's attack was about 2800 and they only had about 800 HP + 400 healing effect.

Another clear example:



And what is really making me mad:
One of my main characters is Golden Son with Freezing talismans, he have ATK 900 and Magic 700. So his physic attack is about 3 times 500, so marked enemies receiving about 1500 physic damage, but PLUS 1500-3000 HP because of strong additional True damage.

Before Golden Son attack:


And after 3x500 physic + 3x700 true damage:


As you can see - left enemy have more HP than before!

It's just driving me crazy. I'm using Axis Bomber attack as last on my turn, but next turn I'm starting with marked enemies that I'm healing with a strong attack.
Using Axis Bomber is very important in my strategy since his passive ability increases Accuracy so the Golden Son have more chances to freeze and burn all the enemies.

Just another example before and after Golden Son's attack:



I hope I've made good examples and description of the issue.
P.S. Don't judge me for mistakes in this post, I'm from Ukraine and probably don't have enough practice in English.