overviewmap markers issue

Hi

I am using the following shortcode
[overviewmap latlngs=overview-latlng category=4 show_thumbnails=true]
to show markers coming from the two posts in the category with id=4 and latlng defined as ACF in the post

When I use debug=true I can see the two posts in the table attached to the map, but when I remove debug I only see the marker of the second post positioned at the coordinates of the first

Two posts have very similar coordinates, here they are
lat=44.306012826238614 lng=8.223038610506068
lat=44.306012826238600 lng=8.223038610506060

Is this problem related to the very similar coordinates of the two posts or am I doing something wrong?

Thanks