Zoom control not properly shown

Same issue reported
here and here
Fingers crossed …

This is a known issue on responsive themes, see also:
https://stackoverflow.com/questions/7471830/google-maps-api-v3-weird-ui-display-glitches-with-screenshot

You use the following CSS to fix the issue:
https://github.com/pronamic/wp-pronamic-google-maps/blob/2.2.8/css/fix.css

Ok, thanks. But why not include the fix in the plugin-code?

We can’t add fixes for every theme to the plugin code. It would be nice if Google adjusted the styling of their maps to make it work better with responsive websites.

Ok, I agree