I cannot “save files” to WD My Cloud EX2 Ultra using the Files App on either iPhone or iPad. My work around so far is to “share” the document, then it will copy okay to the EX2, if I try to Save via the Files App, it will not save to the drive. I can only assume the mapping is not correct for OS5 and Files App.
UPDATE 113020. After a “power-off” and restart it now works as expected with iOX devices. Just rebooting did not correct it, required a power off and unplugging the EX2.