I bet the flap at the tail of the roll wasn't wound tight enough or that there was a wrinkle in the paper backing.
Assuming this is true, the solution is to make sure you wrap the tail nice and tight then fasten it down well.
If the adhesive band doesn't hold the tail tight a piece of tape will help.
If you need a safe place to keep exposed 120 format rolls, save the box they came in.
They're not perfect but better than nothing.
Aside from a little extra protection, they give you a place to write notes.