https://www.youtube.com/watch?v=IUYLySgDsHM

Please fix this, this seems to work on 1.18.1 on the latest version of the plugin, oof.

Hi, we won't have time to fix that in the short time, but feel free to contribute, this is an open source software!

I fully understand that, but perhaps as a short-term fix, could the item be changed to redstone until this bug is fully fixed? That way the damage is mostly contained and barriers, being an illegal item, are not distrubuted to playerbases by dupers.
I unfortunately don't know any java so I'm not sure as to how to do this myself...

For others who have this on their servers, you can negate the - imageonmap.rename permission temporarily to circumvent the dupe. (while still letting players manage maps)

I fully understand that, but perhaps as a short-term fix, could the item be changed to redstone until this bug is fully fixed? That way the damage is mostly contained and barriers, being an illegal item, are not distrubuted to playerbases by dupers. I unfortunately don't know any java so I'm not sure as to how to do this myself...

Feel free to open a PR, I'll merge it happily :)

why not just commit it yourself?

i had the same problem and i found a temporary fix for it,
you just remove the permission to use /maps command, if the player cant access the GUI using this command; they cant get illegal items.
i used Luckperm for that but you can use what evet you want.