TYPO3 Core

Setup:
- 9.5 installation with 2 sites
- Both sites have 2 languages: Dutch with language-id 0 and English with language-id 1
- English has fallbackType: free

Trying to:
- Translate a page and its content elements to English

Problem:
- There's a content element on the page which has IRRE relations, these are not being translated or copied correctly

For translating content, there are 2 options: Translate or Copy, the outcome of these options:
- Translate: content elements get translated, but the IRRE relation does not. This results in a weird view where the element gets displayed twice: once as the original element and once as an element that can be translated
- Copy: content elements get translated, but the IRRE relation does not. This results in the same related element being used for both languages (which of course means that editing the relation in English also affects the Dutch language).

See screenshots:
1. This is the situation in the Dutch language, relation has uid=33
2. This is the situation in the English language when using "Translate", both relations have uid=33
3. This is the situation in the English language when using "Copy", relation has uid=33

I'm not able to pin down where the problem could be, tried to analyze the actions within the DataHandler and TcaInline but no result.