trying to use an existing named LOCATION
Ah, that's important. You are trying to set coordinates from a previously stored location.
Because in your log file (somewhere above, we really should have created a proper bug report for this, not mixing it into the general "IMatch 2018 is here" thread) IMatch reports problems loading stored locations from the database.
When you look at your stored locations in the Map Panel, do they look OK?
Are they filled correctly? Maybe make a change so they are stored again in the database. Then retry.
Keep / attach the log file from that session.
If the problem persists, I would need your database here. Or at least I would need to send you instructions on how to extract the settings from your database file so I can look at them here. Maybe something is broken in the stored locations...