I have/had hardware acceleration enabled.
Browser is: Google Chrome 45.0.2454.101 m
And it doesn't depend on clicking on the ruins & trees/tree-groups that are randomly placed on page-loading, you can click everywhere on the play-screen ...
It is not reproducible immediately on/after page-loading, it seems you have to wait until a certain number of 'normal' pedestrians 'disappear'/'vanish' from the streets ... maybe they don't 'disappear'/'vanish' at all but remain in some 'cache' until being re-used in the streets of the city.
But they also re-appear from there on clicking and stay on the indicated place while mouse-button is pressed ... sometimes you've to press mouse-button for a longer period (1 - 2 seconds) to let them appear there.