When physical stacking ports go down and your stacking cables have been tested then you simply have a crashing switch and are in need of an RMA.  That support engineer shouldn't have left you by yourself and should have helped more. I suggest you call in about the case and friendly ask for an RMA. Do know that MS 410's are practically no longer in supply and the chances they will give you a C9300 variant instead is possible.  That would be a C9300-48S.  In that case make sure they replace both stack units since you cannot stack a C9300 with an MS410 obviously.  And they will have to convert your licenses. I recently had a simple issue with a MS410-16 stack and they replaced it with C9300-24S switches.  And had those issies where they only replaced one at first ;p. ... View more