when you place a map, it consumes 2 maps, if your only holding one it fails to place.
splatter maps are ok, effects standalone maps or single parts of splattermaps
does not effect maps if placed from off hand
does not effect normal in game maps only image to map
does not effect players in creative, only in survival, i think this could be why it wasnt able to be reproduced?

rolled back from 4.1.2
continued in 4.1.1
4.1 used 2 maps still, but wouldnt delete a placed map when you only held one
4.0 works fine
using java 11
server is behind waterfall (bungeecord)
tried removing every plugin besides essentials
useing paper, tried a 153 86 old version and current version
and the panel is pyrodactyl

if you want access to a server its happening to for troubleshooting
i offer my test server, can give you access to the web console

Fixed in 4.2.1. This issue might be there since a long time, or something changed on spigot/paper/minecraft side that we are not aware of. See https://github.com/zDevelopers/ImageOnMap/releases/tag/v4.2.1

Thanks for this detailed walk-through! What is your Minecraft version and server platform (Spigot, Paper, …)? The server itself, not the Bungeecord network

Thanks! We may know the cause, we'ill investigate when possible :) .

honestly im like wow i forgot to mention we are using 1.16.5 out of everything i wrote down
and we are using paper its mentioned in the above post
and just to correct the last post, we are actually using waterfall for bungeecord in case thats somehow related