Hi!
Thank you for your effort!
I can reproduce it on all of these machines:

My laptop: Intel Pentium 2020M, Windows 10, Anaconda Python 3.7.6/3.8, pre-compiled PyTorch 1.3 from https://anaconda.org/pytorch/pytorch

Intel® Core™ i7-4790K, Arch Linux, Python 3.8, PyTorch 1.3.1 compiled with GCC 9.2.0
Intel® Core™ i7-7700K, Arch Linux, Python 3.8, PyTorch 1.3.1 compiled with GCC 9.2.0
Intel® Core™ i7-5820K, Arch Linux, Python 3.8, PyTorch 1.3.1 compiled with GCC 9.2.0
2x Intel® Xeon® E5-2620, Arch Linux, Python 3.8, PyTorch 1.3.1 compiled with GCC 9.2.0

I set REQUEST_GRAPH_DELETION = False and TEST_REPEAT_COUNT = 10000. To increase the likelihood of errors, I run other processes while testing, e.g. a CPU stress test or a training experiment.
It seems that the error rate is the lowest on the 4th machine which has most CPU cores (12 logical cores) among the i7s (less than the machine with 2 Xeons). With stress --cpu 6 running in parallel with the test, I get an error rate of about 0.001.