404 error due to permalinks

Hi!
I was wondering if someone could help. I run a bilingual blog using WPML and I keep getting a 404 error on the Home page, as well as in some (not all) categories. The only way I’ve managed to solve this temporarily is to go to Setting > Permalinks and save. No changes were made.
This. happens randomly, without me changing any permalink settings beforehand, or even updating any post.
What am I missing?
Cheers,
Paula

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