https://pastebin.com/3i19M4ai
I'm not sure if ff was the reason for the crash. I've never had this happen before and it seems like a random rare thing.
In game I was doing alot very quickly.
A creeper had just recently spawned inside my basement so I tried to lure it out and kill it. (Fml) it came out and I couldn't kill it fast enough so it blew up knocking down a wall.
I fixed everything then ran quickly to put away materials and when I opened a chest it solid ctd with no delay and still saved everything.
Trace referenced two other mods as well but ff was affecting them directly if I am not mistaken.
Regardless I figured that you might want to check it out.

That is a curious one, as it could actually be my fault...

Added some code to try and detect this to FoamFix 0.8.0.

I forgot to mention that I did sleep just before fixing the house in game. Considering my jvm flags it is entirely possible that the initial chunk load was delayed when the sleep cycle finished. I have been experimenting with flags to see if I can squeeze more out of my game and that particular combination works amazing until I reach 90% allocation at a steady level. It is possible that the sudden burst of loading after a ticking lag (which I've had this happen where an entire day passes in game in code but then renders in an instant) tesselation error could have come from the block state still trying to keep up visually but rendering out of bounds due to the metaphorical "momentum" of the code.
Like slamming on brakes at a red light to stop but you run the light anyway?
Just wanted to share a thought I had in general. Who knows maybe you can catch some inspiration from this. Had to type it somewhere.