After many years of use, the status lamp went yellow and harddrive fix was needed. I followed the excellent instruction step by step including the tips from community regarding the small connectors. Used a magnifying glass for that operation and iFixit tools. The most fiddly part was disconnecting the base, take it easy with that. I went for a Seagate 6TB Ironwolf NAS 256 MB 7200RPM HDD. Only minor trimming on one side of the rubber pads bottom and top. No pre formatting needed, just change of hard disk in the TC meny.

Works perfect!