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New iMac drop Wifi connection when running Time Machine


macrumors newbie
Original poster
Nov 13, 2019
I have a strange issue with a new iMac (refurbished 2019 model 5k 27") running Catalina: Once I try to start a Time Machine Backup and it's status changes to "Preparing Backup…" the Wifi connection drops and the backup cannot be created. That happens every time I try to create a backup (either via menu bar "Backup Up Now" or via "tmutil startbackup" on Terminal) leaving me effectively unable to create backups for the machine. The backup destination is on a MyCloud EX2 Ultra NAS via SMB. The very same backup method works just fine on a 2017 iMac running High Sierra, so I guess it's a OS bug or anything like that.

The Wifi connection keeps running (I ran ping on Terminal for testing purposes and it had no problems for at least an hour) as long I don't trigger any TM backup.

Has anyone seen this before? If so, any suggestions how to fix that?
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