Ocasional memory manager error on launch

I have a renderer based loosely around the last of the OptiX advanced examples.

8 out of 10 times I launch and it works perfectly fine with no issues or errors, but randomly every so often I get a memory manager exception on launch.

I am running the denoiser as setup in the example.

I’m not sure what to go on. I run the program again and again in the same shell without closing it, so maybe that has some effect.

^C[106432.527489] [WARN]Received Interrupt signal.
Unknown error (Details: Function "RTresult _rtContextLaunch2D(RTcontext, unsigned int, RTsize, RTsize)" caught exception: Assertion failed: "!m_launching : Memory manager launch is already active", file: /root/sw/wsapps/raytracing/rtsdk/rel5.1/src/Memory/MemoryManager.cpp, line: 962

On Linux CentOS7, running optix 5.1