I have not been able to reproduce these issues. Can you please provide a ready to run sample project by email (mailto:help@tmssoftware.com) that demonstrates the issue so I can further investigate this?
Can you please make sure the markers are removed from both the Markers collection and the map? For example, when using the ClearMapMarkers call, the markers are only removed from the map but not from the Markers collection.
If the problem persists, please provide a ready to run sample project that demonstrates the issue by email (mailto:help@tmssoftware.com).