Product sitemap not found (5000 products)

My sitemap only shows about 120 products of more than 5000 (Woocommerce converted from WPEC at some point)

https://www.epal.is/sitemap_index.xml – Main sitemap works
https://www.epal.is/product-sitemap1.xml – Works – shows 110 products
https://www.epal.is/product-sitemap2.xml – 10 products?
https://www.epal.is/product-sitemap3.xml – Not found
and all other product sitemaps are also not found.

I have 1000 entries per page, but I’ve tried setting to 100 entries per page and it did not change much. I just got many more sitemap links that did not work.

I have Super cache enabled with necessary exceptions:
sitemap(_index|[0-9]+)?\.xml
I even put “.xml” as an exception and disabled caching, but it did not change anything.

Any ideas on what I can try to fix this?
Google was finally going to index my products when I found this out.

https://www.ads-software.com/plugins/wordpress-seo/