Very puzzling. I normally might have said something like that it might be your game crashed and the file didn't get written to correctly during the shutdown process. But I tested it and the file uimapmarkers.def is written to immediately after you create or delete a marker (not subject to error during crash). So sorry, my official answer is *shrug*. The only other possible scenario I could forsee a possible conflict is if you are dual logging on the same game folder. But even that seems unlikely, but possible. All I can suggest is make frequent backups of your Prefs\GameServer_CharacterName\uimapmarkers.def file. A quick and easy way is to type this into notepad:
Code:
Copy uimapmarkers.def uimapmarkers.def.bak
Save as "backup.bat" Yes add the quotation marks in the file name so it doesn't get saved as backup.bat.txt
Repeat and make another file:
Code:
Copy uimapmarkers.def.bak uimapmarkers.def
Save as "restore.bat" Yes add the quotation marks in the file name so it doesn't get saved as restore.bat.txt
Put these two files in the same folder. You can create a shortcut and put it on desktop or wherever. One click to backup.bat will backup the file. Another click to restore.bat will restore the file whenever needed.
Until the reason is figured out you can save yourself some work of redoing the missing markers when it does happen
One last thing I was wondering about. Do you ever add/delete markers manually by editing the file in notepad? If so, if you miss one of the brackets {, everything afterwards will not show up in map. I've done that myself a few times.