Hi,
1) Could you, please, update theme to version 6.2.9 + Core plugin to 2.1.3 (WP Dashboard > Updates > Check again button) this bug was fixed in the latest version?
2) After that Sync existing translation with updated pot file https://xstore.helpscoutdocs.com/article/103-translation-files-update and check if Related products string of theme translation file is translated.
These actions should help you.
Regards,
Hung PD