LEAK: ByteBuf.release() was not called before it's garbage-collected

We’re having this issue on our server with a leak. Everytime a player joins our server, we have a leak.
I’m informed that Sponge was the cause of this. We’re running spongeforge-1.12.2-2768-7.1.4.jar.
I’ve tried to download a more recent Sponge, this was spongeforge-1.12.2-2768-7.1.5-RC3512.jar but this one was giving the same error.

The leak seems to be causing ram issues. After 2-3 hours the server crashes because of it.
In case it influence anything, this is the java settings we’re using:

java -Xms2048M -Xmx{{SERVER_MEMORY}}M -Djava.util.concurrent.ForkJoinPool.common.parallelism=16 -XX:+UseG1GC -XX:+UnlockExperimentalVMOptions -XX:G1HeapRegionSize=64M -XX:MaxGCPauseMillis=50 -XX:+DisableExplicitGC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:G1MixedGCLiveThresholdPercent=50 -XX:+AlwaysPreTouch -Dio.netty.leakDetection.level=advanced -jar {{SERVER_JARFILE}} nogui

Pastebin Leak Error

It would be lovely if someone can give me more insight on the issue and can tell me how to solve it or what to try. Thanks for reading.

Seems to be actually Tropicraft based on the paste.
And according to ERROR · Issue #296 · Tropicraft/Tropicraft · GitHub this issue was already fixed for Version 7.1.7

Thanks alot for your reply. That seems to be it indeed. I wouldn’t have been able to find it myself. Thanks!