Make it easier to find duplicate MACs

The issues page has a “Duplicate MAC” issue that gets flagged.  However, both miners aren't flagged - only one is.  This makes the process of finding the actual duplicate very manual.  I have to copy each MAC address individually, filter by it, which then reveals both of the miners, and then I can manually delete one.

An easier way to find duplicates would be nice.  The filtering that happens now just makes for a lot of follow-on, manual work, since only 1 of each duplicated pair is revealed.