Internal links into sections have broken

We have documentor 1.5.4.1(paid) installed on WordPress 4.8.5 and we are getting 404 with internal sections links, I think it started to happen after our last worpress upgrade.

I have tried this:

– reset the permalinks
– searched the links on the database piting to old site and move it to current url site
– I deactivated and reactivate the plugin once

it didn’t work

Thanks for you help

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