[mpiexec@node00] HYD_sock_write (../../../../../src/pm/i_hydra/libhydra/sock/hydra_sock_intel.c:353): write error (Bad file descriptor)
[mpiexec@node00] cmd_bcast_root (../../../../../src/pm/i_hydra/mpiexec/mpiexec.c:147): error sending cwd cmd to proxy
[mpiexec@node00] stdin_cb (../../../../../src/pm/i_hydra/mpiexec/mpiexec.c:324): unable to send response downstream
[mpiexec@node00] HYDI_dmx_poll_wait_for_event (../../../../../src/pm/i_hydra/libhydra/demux/hydra_demux_poll.c:79): callback returned error status
[mpiexec@node00] main (../../../../../src/pm/i_hydra/mpiexec/mpiexec.c:2064): error waiting for event

[mpiexec@host1] wait_proxies_to_terminate (../../../../../src/pm/i_hydra/mpiexec/intel/i_mpiexec.c:389): downstream from host host2 exited with status 255

the host reboot;
an unexpected signal received;
out-of-memory manager (OOM) errors;
job termination by the Job Scheduler (PBS Pro*,  SLURM*) in case of resources limitation (for example, walltime or cputime limitation).

Check the system log files.
Try to find the reason of the
hydra_pmi_proxy
process termination and fix the issue.