Although a rare case, I did an unusual edit, and observed this behavior:

• Open OsmAPP editor for a feature (attributes displayed in modal window) - version 6 retrieved
• In a separate editor, updated the attributes of the same feature and saved it to OSM. - saved as version 7
• Return to OsmAPP, add a new attribute to the already opened editor. Save - saved as version 8, but based on version 6
• Result: I lost the attributes added in the second editor, which was already saved in OSM but newer than the attributes loaded in the OsmAPP editor.

It might be a good idea to re-check OSM for any changes since the last time data was retrieved, before saving new edits, and potentially losing contributions by editors.

Here's a visualization of the tag changes