There is a table on the devices called etsysConfigMgmtChangeTable. This table is responsible for performing operations that include resetting the device, firmware upgrades and config upload/downloads. There are 5 slots available in this table. If they are all in use then no other action can be performed unless the entry is cleared. In normal operating conditions when an action is completed the table entry is automatically removed. If there was a failure for some reason there is the possibility that the entry will not clear.