While a software update is in progress, navigating to the Administration->Version->Updates page in the Control Center shows the "Download Only" button as enabled even though the update is listed as "In progress." Clicking the "Download Only" button in this state generates the message "Another Software Update is currently running. Cannot perform the request."
This is a cosmetic defect and has been addressed in SMG 10.5.2. Please update when able.
Selecting the "Download Only" button while an update is in progress will cause no harm and not interrupt the update.
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