I think this might be a manifestation of this behavior - Bug report: Newlines duplicated within fields - #6 by dae . You have all that “invisible” header information in your field (as opposed to your template), so if you edit the note in AnkiDroid, it is re-parsing the newlines as linebreaks <br>.
Possible solutions for the time-being –
- Don’t edit notes with complex HTML in AnkiDroid
- Settings > Advanced > Workarounds > Replace newlines > toggle off