Player markers aren't visible on maps placed in item frames

The bug

Player markers are not visible on maps placed in item frames.

Steps to reproduce

1. Create a map
2. Clone that map
3. Put one of those maps into a frame
4. Look at the map in the frame
5. Notice that there's no player marker visible on it even though it's visible on your copy of the map

Original report

the following markers do not show on the map when you place the map in an item frame:

Light Gray (red player marker)
Pink (white player marker)
Cyan (blue player marker)

this affects the named markers as well