I tried to checkout the "initial" branch (which you referenced in your Renderer.java link), but that fails due to incorrect loading of the shader text (you only load the first line of the shader file).
Then I tried the "master" branch, but there you don't do anything in the Renderer class.
So the question is: Is there any version in any branch or commit that reproduces your problem?
My advice however is: Use
LWJGLX/debug by downloading it from
https://lwjgl.org/customize (select any release version and check only "LWJGLX/debug" under "Addons"). This will give you a zip file containing lwjglx-debug-1.0.0.jar.
Then you need to run your application with the JVM argument "-javaagent:<dir>/lwjglx-debug-1.0.0.jar", where <dir> is the directory you extracted the lwjglx-debug-1.0.0.jar into.