It might be the Jet Stream that is knocking them over when they are coming down off the Cloud.
Most likely, it's lost the metadata that Windows stores alongside files on the system.
Windows can store information about the files, which isn't actually in the files themselves. Uploading the file to the cloud and downloading it again loses that data, so Windows doesn't know which way up to display the pictures.
That, although boring does make a lot of sense. Thanks. Its a pain though and would put me off losing the original source data.