www.dl2rum.de

When my callsign showes up in the DX call window, it shows I'm 755 miles away at a heading of 138 deg. That is approximately the location of the previous holder of my current callsign.

Where does the DX Spots window reference it's information from? I have made attempts to update the location of my callsign to my current information.

When I type my own callsign into the logbook window, it appears to be correct (1 mile away).

See the map below. To show dx-spots, RUMlog uses the default DXCC location (red prefixes), sometimes (hardcoded) a modified location (magenta prefixes).
When you enter a callsign, the known location from the log or from qrz.com will be used.