Issue Description: *When I restart my server, there seems to be an issue with the Marker writing (especially with signs), as they disappear after the server starts back up again. I don't know the exact cause and I don't know how to replicate it, but I dunno how its happening.

One unique thing I did find was that in my timings report, a LOT of ticks happening for the value "dynmap::Task: org.dynmap.markers.impl.MarkerAPIImpl.DoFileWrites (Single)", so I'm guessing it's having a problem writing the file for the marker position, which then resets after a restart.*

• Dynmap Version: v3.2-beta-2
• Server Version: Purpur 1.17.1 latest build (almost identical to paper just with some extra configuration)
• Pastebin of Configuration.txt: https://pastebin.com/55DG5iNn
• Server Host (if applicable): Dedicated server
• Pastebin of crashlogs or other relevant logs: N/A
• Other Relevant Data/Screenshots: N/A
• Steps to Replicate: N/A

[ X ] I have looked at all other issues and this is not a duplicate
[ ] I have been able to replicate this

Duplicate of #1936