Created an MR that addressed this issue, also updated IS, steps to reproduce and title.
- 🇦🇹Austria fago Vienna
I still think we need to do what I was writing before:
We'd have to forward the selected langcode. So we must pass the entity language as $langcode when calling this.
Next, the bug might exist in other processors also. When we fix it, we should fix it in all of them.
For 2.x I think it's good enough to fix this with the call-out to the global or even not fix it -> 3.x is the main branch now.
For 3.x we should fix it properly.i.e. we must extend our API to accept an optional $langcode parameter, so we can pass it on during processing *explicitly*. This is what core does during rendering as well. I guess this means we need to adjust the processors to do so. A new optional $langcode = NULL parameter is no big change, since it keeps BC when the interface was implemented exactly before.