I have successfully transferred a full size photo from my iPhone to the WMD with no downsizing. But, upon transferring that photo to iPad (and confirming it’s still full size), then transferring back to WMD resulted in a downsized photo.
MANY attempts to transfer photos from my iPad, and ALL are either downsized or corrupt transfers. Retransferring photos that were corrupted the first time can result in successful (though still downsized) transfers.
I downloaded the iPhone version of the SanDisk app to my iPad, and with that I can transfer full size photos between iPad and WMD in either direction. So, the bug appears to be isolated to the iPad version of the software.