java.lang.StackOverflowError and massive stacktrace error when trading

[therbz]

/version
[22:24:47 INFO]: This server is running Paper version git-Paper-108 (MC: 1.16.1) (Implementing API version 1.16.1-R0.1-SNAPSHOT)
[22:24:47 INFO]: Checking version, please wait...
[22:24:47 INFO]: Previous version: git-Paper-101 (MC: 1.16.1)
[22:24:47 INFO]: You are 3 version(s) behind

/version TradePlus
[22:25:32 INFO]: TradePlus version 3.75
[22:25:32 INFO]: Author: Trophonix

Java version 11
OS Ubuntu 18.04 LTS

What happens?
When two players finish a trade, after the anti-scam countdown, there is a massive StackOverFlow stacktrace error thrown into console and the GUI bugs out. It seems that the players still receive the items as usual though.
The error: https://hastebin.com/holanoheru.bash

Intended behaviour
The GUI shouldn't bug out and this error shouldn't happen.

How to replicate?
For me, all it takes is two players trading anything for it to happen.

[therbz]

When I shut down the server, this is what I get https://hastebin.com/holonuxesi.php
Edit1: No errors on startup.
Edit2: Restart did nothing to fix it.

[leviem1]

Can confirm it's happening to me too on git-Paper-135 TradePlus version 3.78

Current workaround is to disable logging.