Problem with transaction for adding translation - new translation is based on last created translation, not on default or chosen by user. Or at least it looks like this.

Prerequisites

1. Content type with some translatable and non-translatable fields
2. Content item of such type
3. Three enabled languages

Steps:

1. Go to Content > Content structure > //content item from prerequisites//
2. Click Translation tab
3. Click +
4. Select language
5. Fill form and click Publish
6. Click Translation tab
7. Click +
8. Select language and base language same as default

Actual result:

Fields has values from first translation, not from translation selected as base.

Expected result:

Fields has values from translation selected as base.