On servers, maps will stop updating after they have been in hell. You don't have to have opened them, they could have just been in your inventory. When you resurface to the over-world, the map will have froze and so will your marker. The only way to have the map update again, is to re-log.
As you can see, I am standing on a platform where I can AFK for better drop rates on my mob farm(photo1). The map is working but as I enter and leave the nether, (photos1&2) the map still currently says I'm at that position (photo3). Until I have just re-logged, it only works (photo4) This was done in a private 14w04b server. This bug is affecting me in a severe way, due to the fact that my computer is old, and takes forever for me to actually log in.

_{Mod edit: Added description of MC-79225 :}
There are some unresolved and/or abandoned bugs for this issue. I was doing a bit of programming using map packets, and eventually found out that the client ignores map update packets once the dimension has been changed.

The easiest way to reproduce (singleplayer or multiplayer):

• Create a map for your current area
• Create a nether portal
• Go in the nether portal and then return back
• Notice your map no longer updates

Any update packets sent that corresponds with the damage value that corresponds with the map created at the start of the above process is ignored after dimensions are changed.

Logging out and logging back in (or quitting to title on singleplayer) fixes the issue, but is a poor temporary fix.

Also, it's worth noting that every single map ID that the player has handled packets for will no longer update, not just the single packet in the current area.

Notes:

• You do not need to bring any maps with you into the nether to trigger this bug.
• When the dimension is changed, the map's canvas is cleared on the client's side to all zero pixel values (impossible without modding the server).
• Once the map is updated with any packet that corresponds to its ID, the client displays the last data from when it originally worked (before dimension change), and will not change, and will not show any data from any new incoming packets.

Code analysis: https://bugs.mojang.com/browse/MC-46345?focusedCommentId=295843&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-295843