I told it to manually do it when I installed 5.1.
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Dear user,
A new version of DSM has been downloaded and is ready to install. Please sign into backup and go to Control Panel > Update & Restore to install DSM 5.2-5565.
Sincerely,
Synology DiskStation
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Hoping the dev team gets the bootloader they have had ready out the door so we can all benefit. Hurry up with that testing!