Marks on negatives - Fridge/freezer storage

Hi everyone. Just started scanning again and getting the same marks that I had on previous batches and wondering if anyone can help.
They are always in the same top-bottom orientation and I’m 100% sure it’s not dust.
Tried 2 different scanners and visible on both.
The attached pic is a 100% screenshot. This one does not have IR filter on the scan. This improves it a fair bit.

This is 35mm Portra 400.

The only thing I can think of is that this is due to me cold storing the film (fridge/freezer) and not letting it get to room temp slow enough.

Wondering if anyone has had similar issues and can shed any light on the problem?

Many thanks, Craig