Breath mark: automatic placement does not deactivate (MuseScore 3.0.2+dev)

Steps to reproduce this e.g. in a polyphonic staff (see file)
1. assign a breath mark to a note
2. Disable automatic placement for the breath mark.
3. Use the inspector to move the breath mark to a note of the second voice of the same staff.

Observation: the position of the breath mark still influences the position of other objects. Moving too far leads to extreme stretching. The best way to reset this is to delete the breath mark.

By the way, it would be great to be able to attach breath marks to a voice other than the first one and not have to move it at all. The same applies to dynamics, lines, etc.
(already had another novel-like post about this: https://musescore.org/en/node/283095)