URL ‘redirect’ + 404 on homepage

Hi,

For some reason when switching the homepage from NL to FR he adds a ‘1’ at the end of the URL resulting in a 404.

https://eye-t.be/ = NL
https://eye-t.be/accueil/1 = when switching to FR but should be https://eye-t.be/accueil/

I really can’t find the solution.
When using standards permalinks all works fine.

W3 total cache is installed