Sending Command Issue is something that can popup randomly in sessions in various quantities. It completely stops the workload causing stuck sessions.
A probable Fix is found, its most likely due to the DDE (Direct Data Exchange) exac feature in windows. To fix this or verify this check the registry at HKEY_CLASSES_ROOT\.doc(Extension name i.e. xlsx or ppt)\ and find the application type name (I.e. word.doc.8). Search in the same area (HKEY_CLASSES_ROOT) for the application type name extension (I.e. word.doc.8) when found remove the entry DDEexec (or similar) or remove the /DDE command from execution string. Make sure %1 is always in the string.
This is not a 100% fix but we have seen improvements when this is configured.