>>3414258>I've had backing paper issues with room stored Portra and Ektar barely past the expiration date.This is a recent Kodak only problem
https://www.photrio.com/forum/threads/kodak-120-film-backing-paper-problems-emulsions-affected.137251/Basically they changed their backing paper a few years ago, causing problems for anyone buying film outside the UK. Kodak eventually fixed this by switching to glossy backing paper, starting from the batches produced in 2018, pic related.
ATM I'm using Fuji until the shops around here start selling Kodaks with the new emulsion numbers. It's going to take a while though, especially with portra 160/800 and ektar because they're not as popular as portra 400, because old stock is still slowly being moved from distribution channels.