The test harness supplied with the library allows each library unit to be compiled and simulated in isolation. When the library unit is instanced within your design, the compilation result might differ from the result obtained with the test harness. This might be because compilation of your system might need arguments not present in your system.
Search the Makefile provided for UUT_TARGET_COMPILE_ARGS. For each library element, there can be compile arguments used to avoid errors or to improve performance, that is, specifying memories to be on separate banks to avoid wait states. These arguments will likely change with each release as the compile tool changes with each release.