Well I’ll try do describe what happened, step by step:
1) I was running toward a fallen enemy maiden
2) I got hit by another enemy maiden fireblast, and at the same time, by a dragon firebreath.
3) I managed to hit the button to execute the fallen maiden, the damage wasn’t “computed” just yet it seems.
4) When my maiden started the execution animation, she disappeared, became invisible, yet her hitbox seemed to be there.
5) When the execution ended, my maiden reappeared there.
We are going to close this issue as we like this effect. It allows you to flash dash into execute and revive or harvest (new mechanic in mission mode) and conduct the execute/revive/harvest while invisible. This gives an advantage if you are able to skillfully pull this off. You were invisible because you executed while flash dashing.