I tried with RHEL 6.6 but I wasn't able to reproduce.
My script ran for log time.
I can try to test with different machines, but you were able to reproduce in VM
as well. So i'm not sure it will help.
BTW HPC machines are usually diskless. Is it your case as well?
because it is not supported to have sssd cache (/va/lib/sssd/) on nfs.
sssd cache is on a local disk.