Markers sometimes change their center point
On a fresh page load, the park markers are attached at the tip to the appropriate GPS point location. However, after an undetermined series of events and playing with the page, they seem to lose their attachment to that correct location, and as you zoom out, they no longer mark the center of the parks.
Can't figure out a reliable way to reproduce it.
It sounds like it could be a leaflet issue, and is probably worth updating the leaflet version currently in use.