The effect is the same if markerclusterer is not used.
I suspect the problem is that the click listener is added "manually" to the marker instead of specifying "on-click" on a marker directive but how to use markerclusterer in that case. Even if if try to use a marker directive it's way to slow for thousands of markers.
check out this plnkr: https://plnkr.co/edit/qkrcSe1urtn2XAF3bMGA?p=preview no matter which marker you click, it thinks it is the last one.
The effect is the same if markerclusterer is not used.
I suspect the problem is that the click listener is added "manually" to the marker instead of specifying "on-click" on a marker directive but how to use markerclusterer in that case. Even if if try to use a marker directive it's way to slow for thousands of markers.