I have owned a 2TB My Cloud for about 6 months and found that all the WD firmware versions are buggy. I use my WD as a replacement for Dropbox and access the files from two PCs. I am an amateur photographer and upload photos almost daily, and this is where the problems start (IMHO). As soon as files are uploaded, the WD starts scanning but it seems unable to update the database it keeps, and eventually it crashes. So it starts a rebuild from scratch, and as I have a large number of photos it takes several hours. While it is doing a rebuild it is so busy that it drops off line, so any file copying or (more importantly) moving it was doing is stopped midstream. This leads to data loss.
I got fed up waitining for WD to sort the problems out and I have just removed all their software using this method here. Since doing this last Friday I have tried hard to make it fall over and I can’t, copying/moving files between the NAS and 2 PCs simultaneously. Previously I didn’t have to try, just using one was enough.
If you do install the clean Debian image (i.e. just a basic Linux PC system) you will invalidate the WD warranty and end up with just a disk on the network (i.e. a NAS server!). You will lose all the WD programs but there are plenty of free alternatives which, again IMHO, perform better, some having more functions/control to boot.
I wrote a script some while back and recently uploaded it to P33 of the thread above. The WD software added over 150,000 thumbnails to my files, videos and photos, both in private shares and the Public folder. For some, it created 4 different size thumbnails! The script will find these, count them and put the filenames and locations into a file. I don’t recommend deleting your thumbnails if you are running WD firmware (as they will be recreated), but you can at least see what the firmware is producing and possibly why the performance is so poor. There’s a screen print on P33 of that thread.
Hope this helps.