I just updated from Joomla 3 to Joomla 4.3.4 and Hotspots 6.0.12. I decided to experiment with a new icon for a category (BSD-2000). Originally the marker graphic was located images/com_hotspots.hotspot/orange-pointer.png. After I changed it, any location with that icon will no longer display. Tried to change it back and the icon shows broken link and will not display.
Attempted to change it to an marker from the sample icon set "Hospital", and I can change it, but the category will still not display. Opening up hotspots and looking at the filter (see image) the file path for the working Blue marker icon is /images/com_hotspots.hotspot/blue-pointer.png, the broken Hospital marker Icon image path is /[sample]/sample/hospital.png