Full output of /ess version:
[05:01:02 INFO]: Server version: 1.13.2-R0.1-SNAPSHOT git-Paper-597 (MC: 1.13.2)
[05:01:02 INFO]: EssentialsX version: 2.16.1.80
[05:01:02 INFO]: EssentialsXChat version: 2.16.1.80
[05:01:02 INFO]: EssentialsXSpawn version: 2.16.1.80
[05:01:02 INFO]: Vault is not installed. Chat and permissions may not work.
EssentialsX config:
https://gist.github.com/EvModder/29cf2c5d52cf6fcf425396cfb76e4c1f
Description
When the length of a line on a [Trade] sign is at or near the maximum allowed length of a line on a sign, EssentialsX will allow the creation of the sign (text will turn blue) but will not allow any interaction with the sign, even if the result of the interaction REDUCES the length of the line in question.
Steps to reproduce
This issue occurs for many signs in our market area, but for a good baseline example copy the following onto a sign:
[Trade]
$15:0
64 gunpowder:256
If a custom currency symbol is set, (in our case, L) use that instead of $ on line 2.
Expected behavior
If it is possible to create the signs, it should also be possible to interact with them, especially if that interaction only reduces the length of the lines on the sign (e.g., buying).
I can confirm that this occurs when using a valid username of 16 characters.
Use the command to find all possible "Short names" for the item on the sign. Unfortunately gunpowder has no other names, but in the case of cooked_beef, "gbeef" is actually one of the short names.
Will not help in all cases, but useful if you're just 1 character space too short. Hope this helps for some of your signs.
Follow up to bradykolson's tip:
in /plugins/Essentials/ there is a file (items.csv or items.json in newer versions), where you can add your own "short names" for items (e.g., add "sulfur" for gunpowder).
Of course, this helps fit longer text on the sign, but doesn't fix the issue of EssentialsX thinking the sign has less space than it actually does.
Thanks for the solution, it works well for the smoothstone:
In /plugins/Essentials/items.json:
...
"smoothstone": "smooth_stone",
"smooth": "smooth_stone", <--- New line
"smoothsmoothstone": "smooth_stone_slab",
...
Now I can use smooth for smoothstone

I think this example could be helpful to someone
FYI, manually editing items.json isn't recommended (and may not be supported at all in the future). You should use custom_items.yml to add custom item aliases instead.
Hi, thank you your help.
Is there somewhere on the wiki or any documentation I can find back this specific information?
This is quite a large problem, if you check the recent bug reports, we figured out this length limit can dupe large amounts of items with the right conditions
@bidetaggle See the examples in the plugins/Essentials/custom_items.yml file.
Could you provide a direct link?
https://github.com/EssentialsX/Essentials/blob/2.x/Essentials/src/custom_items.yml
To clarify: the file should already exist with examples at plugins/Essentials/custom_items.yml in your server's directory (if it doesn't, you need to update EssentialsX or else the feature won't work).
Not sure why this has not yet received confirmed status, as the issue is incredibly easy to reproduce. Also, it is now the cause of another much more serious issue as I have reported in #3384 wherein it is possible possible to duplicate items via destroying a trade sign when the item line is affected by this error.
@BusiedBat306 Please don't bump multiple threads to draw attention to your issue. We're aware of it and will deal with it when we're able to - you don't need to keep bumping it.
@md678685 Was not my intention, apologies if it came off that way. I have replied several times to my own simply because I was discovering more relevant information and wanted to add it to the thread. Likewise, this issue and my own are relevant to each other, so linking them is simply (at least in my mind) the appropriate thing to do.
This is not going to be fixed; apparently the 15 character limit is a feature.
We're not going to remove the limit for the reasons explained in my response to #3392. I'm planning to improve validation to be less frustrating (making creation and interaction checks more consistent), but the limit isn't going to be removed entirely.