Getting her finger bitten or hearing that the smoke in the scene was “sexy”...
The recent filming of Kyungsung Lady had turned into a series of humiliations for Seoyeon that she would rather never experience again.

But, in truth, none of those things really mattered.
Seoyeon almost never made NGs (outtakes), so the staff were more surprised than anything else.
Director Baek Min seemed to regard it as merely part of the process of finding the right emotional tone.

So, there wasn’t any particular issue with the NG itself.
It was just a bit embarrassing, that’s …