Strange bug in diagram legend EA v. 1310

[Richard Freggi]

I am using v13 (eagerly awaiting to update to v16) and I have strange behaviour on diagram legends.  I'd like to know if anyone knows a workaround?
In sequence diagrams I need to color code messages to highlight some business semantics.  I use legend-connectors-filter-tagged values with preset codes in a custom tagged value to determine the message color.
Every time I close the diagram and reopen it, the color coding disappears and I have to reopen the legend dialog to set again the tagged value that determines color.  The legend still shows 'apply auto color', 'apply line' etc. but the filter is not pointing to the custom tagged value any more.  Does anyone have a workaround?  Thanks!!