Solved. It was definitely a bug. I should not be able to go to the gate, but a cut scene should be appear.

Reload the save game was never be a solution. But after some time left it be, I played the game again by going straight to the gate. In previous when the bug occured, I always smashed all the ice.

Not long after inside the ruin, another free fall occured after switching character to the dragon. No fall mechanic around in that map.

So, I'm suspecting that the ice smashing or character switching trigger the skipped cut scene and free fall bug.

If you switch to a character and back quickly and the character passes by a cutscene trigger, you skip the cutscene and on certain ones it means you can’t continue. This is actually used in speedrun for the game on most cutscenes, just not the ones that can’t allow you to continue, this also can clip you through walls/terrain