I think the best way to sum this up is, when holding a mob with the Rod of the Shaded Mesa, while Twilight Forest is installed, ice chunks created by Twilight Forest's Ice Bow and Ice Sword will flicker in and out of existence on the held mob. As far as I can tell, it's just a visual bug, but I thought I should bring it up anyway.

But this isn't an idea, it's a bug. Don't feel like investigating?