The 0x80007045D error is an I/O error, this indicates that something may have gone wrong on a sector of your WD HD or on the ROCK HD itself. Can you please try a few tests here?
If you have a thumb drive and can load some media on it and connect it to the ROCK, does copying tracks from that source work as expected?
Are you able to connect the WD drive directly to a Windows PC and try copying some files to/from it successfully?
Hopefully one of these tests will show us where the issue lies, on the ROCK HDD or the WD HDD and will allow us to gather some next steps. I would also highly advise in performing a disk check on your WD drive while it is connected to your Windows machine.
I have removed the WD HD from Rock and connected it to my Windows PC. The error was reproducable and obviously was caused by a corrupt file.
The WD Disc utility and chkdsk gave no indication of erros on the HD itself.
I have reconnected the HD to Rock now and will observe.
What I find annyoning though, was that the connection from Rock to the drive was lost due to this error. When I did the file move on windows I got the same error, but I could click on “ignore” and the rest of the files was moved without any problems.
On Rock I totally lost my drive, therefore In Roon I had no access to my music anymore. Isn’t it possible to deal with these things in a more user friendly way? I had to reboot Rock ervytime, in order to get access back.