The bug
Player markers are not visible on maps placed in item frames.
Steps to reproduce
Create a map
Clone that map
Put one of those maps into a frame
Look at the map in the frame
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
Related issues
Attachments
Comments


This is working as intended, as those are unused, and player markers. Player markers aren't intended to show up in item frames on maps.

This is not intended behavior creepermagnet, those markers are made from banners, not players themselves, thus those banners somehow don't show up on the map.
I've generalized this ticket; player markers generally don't appear on maps in frames, the fact that banners generate player markers at all is covered by MC-126815.
As @unknown said, it's very likely that it's actually intended that player markers aren't shown on maps in frames; as far as I know, there's code that specifically prevents exactly that.

This issue appears to have been somewhat fixed in the latest version (1.13-pre2 at the time of writing) because now these do show up in item frames (see attachment).
However I have discovered a new issue: although player markers are shown in "framed maps" they don't show any color attributes which are shown when a map is being held:
[media]
What I did here: I like to maintain a "teleport wall" with interesting places. Here I've copied the map ("pick click") I placed a named & colored banner and marked it on the map. As a result the banner shows on both maps, but as you can see the "framed map" doesn't show the cyan text nor does the banner appear in the fully right color.
Hope this can help!

Can you create a new issue for that? that way this is marked as fixed and progress on the new issue can be tracked on its own