Joomla extension producing error "Data column(s) for axis #0 cannot be of type string"

Hello, I am currently testing Clicky in combination with the most current Joomla release on 3 of my web sites and they all produce the same error message in the admin console. Data collection works as the Clicky site shows the results. To me this looks like an issue of the Joomla extension but I didn't get much further with DeConf, the producer of the Joomla module, so I thought I try to see if anyone here may have an idea on where things go wrong.
https://deconf.com/ask/question/joomla-3-6-5-clicky-analytics-dashboard-data-columns-for-axis-0-cannot-be-of-type-string/

Thanks
Thomas