We have been running the plugin for 3 days on a relatively low traffic site. Yet I can see that the data already is very odd.
First, the plugin is not splitting traffic 50/50 - not even close. 77 vs 15 unique visitors. So something is wrong there.
The bounce rate on both is 0%. While that would be awesome, it is absolutely wrong.
If you add up the columns percentages, they are nowhere near 100%. So not every visit is being tracked. 67.5% of page views to the Classic theme, 6.47% to the Modern theme. These should be adding up to 100%.
So why is this plugin not tracking properly?
We use the Google Analytics for WordPress by Yoast plugin as well.