Wouldnt that also force you to remove the device from FMC and then re-add? or would you also have the make the FMC change separately?

You can do this from the FMC under Devices and Device Management select your device to rename click edit, and then select the Device tab. The first section click on the edit pencil and you should be able to rename the device. Dont forget to save and ...

I am having this exact same issue after the 5.4.1.8 upgrade.  I am able to get rule and geo-location updates without issue.  It seems the Security Intel feeds were the only thing effected.