You can tell the volunteers who work at Ttukseom that holds are loose and they will fix them.
I had 1, maybe 2 loose(ish) holds, but nothing bad enough to slip or rotate.
I've been to Ttukseom several times and the wall is pretty solid.
Also, rotating tiny foothold will happen anywhere, even in a gym.
PS you scaled up a wall with your sling and nobody said anything? Strange.