@primoz.rome, it actually had nothing to do with the plug-in, but the editor field type (see my post above for a fuller explanation).
The editor was closing on save if the field editor was set to “Expanded view”, regardless of whether you were using the plug-in to auto-save or manually clicking the save button (as you pointed out). Once we fixed that underlying behavior, both the auto-save and manual save no longer close the editor.
The plug-in hasn’t changed, but now that same version should no longer close the editor (since it wasn’t the plug-in’s fault to begin with, just the editor’s default save functionality).