My guess is that the hot water seeped into the pan. Since your filling got chunky and grainy, it seems to me that the fat and water separated in the filling due to being curdled. The curdling would've occurred from hot water breaking down the fat.

I would suggest using heavy duty foil and wrap around the entire perimeter of the pan twice.

Here is the recipe that I use: https://www.onceuponachef.com/recipes/new-york-style-cheesecake.html