Analog film photography and cameras

Sure I flatten them with books / weights of some sort. It sucks when you're in a hurry though.

Just baffled me that sometimes they're flat, sometimes they are not.
This, and that they are indeed coming from a "rolled-up state" - but across, not lengthwise!

Depends on film and what you do with it. All forms of variables. Faster film warps more, fresh chemicals do that too. If the heaters are off by a few degrees that happens. Pushing it during development does that as well. Luck of the draw really.
The whole across warp generally happens when you cut them up soon after cooling down.
What I notived is you're better off flattening them when they're bunched up in in stretches of 6 or more as opposed to individually.