Bug happens on Windows 10 and Xbox one. This might be the case for other platforms as well.
Some player markers wont show up on the map despite multiple players or are the same colors (Me and my friend both show up as white on my map), and some others say I'm not on their map. We play a world that makes us have to keep an eye on each other so this poses an issue.

Edit: Happens with item framed locator maps as well.