Bug Report

Type /ver NametagEdit and post the output.

version 4.4.0

What version of Bukkit/Spigot/PaperSpigot are you using? Type /ver

Spigot 1.12.2

What plugins are you using? Type /plugins

probaly due to the own plugin, but if needed i will send in private my plugins

Please explain your issue. How do you trigger it?
on this example
http://prntscr.com/m8nf5l
it should had remove the last letter of the name, and not the first

Are there any errors in the console? Please use: https://pastebin.com

no

Your prefix has 17+ characters, after cutting to 16 the last one is &, and first letter was used with the & as a color code combination. As a result, first letter of name disappears.