Ouch. That shouldn't happen.
First thing we can try is earlier jemalloc versions. Could you please try jemalloc.dylib from the LWJGL 3.1.0 and 3.1.1 releases? You can download it from
here, using the "Click to browse..." functionality. Use -Dorg.lwjgl.system.jemalloc.libname=<path_to_jemalloc.dylib> to override the library to load and -Dorg.lwjgl.util.DebugLoader=true to verify that the correct one is being loaded.
If you could also share a minimal program that reproduces the issue, it would be very useful.