This would be a lot easier if it was a single BP.
So, because there each wall is a BP, then we must ensure that the player is crushed / dies only when the 2 walls are “on him” simultaneously.
So, I tried this script in the wall BP, where TileChar is the character and BP_Walls is the wall BP:
Since this code exists in both walls, it will call the Die function twice, so you need to make sure that the player has a DoOnce in that function.
PS: maybe this is a little too much for such a simple task, but I enjoy trying new ways of doing things.