Stability of parellel.foreach inner loop on another foreach

I have written a structure of executing list of command parallelly to multiple devices at the same time. [login to view URL]([login to view URL],//multiple device new ParallelOptions { // multiply the count because a processor has 2 cores //MaxDegreeOfParallelism = [login to view URL]([login to view URL](([login to view URL] * 0.75) * 2.0)) }, keyValuePair => { ...... foreach (string cmd in [login to view URL])//[login to view URL] is list of command that prepare to send over to few devices,[login to view URL] contains device info include ip address of the device { ... //send command //receive response from the device } } Most of the the time, the send and receive response message from devices parallelly work normally, however less stability. If you have idea how to resolve the issue, welcome to bid the job. You are no need to write the send or receive message from device anymore, just need to increase the stability/reliability.