The head on the tombstone often becomes translucent, and the chest near the incident also becomes translucent. When I see the tombstone the frame rate drops so badly and renders a lot of terrain, I can even look for the tombstone through stuttering. Minecraft version: 1.8.9+optfine
That can break GC too
Only tombstones generated after the player's death

Can confirm. Came here to look for this.
Using this mod on 1.12.1 and the gravestone tends to cause a lot of lag.
Even looking into the direction the gravestone is placed causes the frames to drop