For Duplicate Post to be compatible with Polylang the taxonomy post_translations needs to be excluded from the rewrite and republish feature. Polylang has already done this for the duplicate post feature.

The filter duplicate_post_taxonomies_excludelist_filter does not work on the rewrite & republish feature due to use_filters being set to false.

Due to there not being a filter available I have created a patch for myself: wearerequired@0869c1d