Hi Mark. I see a couple of console errors on your site;
Uncaught ReferenceError: jQuery is not defined
main.js:21 Uncaught RangeError: Maximum call stack size exceeded.
I’m not sure what those errors mean, but one guess is an unexpected/unhandled value in the location data. It could also be a conflict with your theme: “ajaxRevslider” is mentioned in the error, which is probably a slider included in your theme.
On another note, have you tried checking for plugin/theme conflicts?
- Disable all plugins except SLP and SLP addons
- Set the theme to something generic, such as WP Twenty Fourteen
- Verify that the map is no longer exhibiting problems
- Try your theme, and check the map again
- Enable one additional plugin and check again
- Keep checking until you find the offending theme/plugin(s)