Why is Facebook cropping my cover photo when it's set to proper dimensions?

[Dolly Dagger]

Created a FB cover photo for a Page with appropriate dimensions (1702 x 630, also tried sizing down myself to lower res 851 x 315), yet when I upload it Facebook crops it strangely: cutting off the top of the banner significantly and some of the sides as well. Facebook also won't let me "slide" the image to adjust it within the frame (as it does when you upload outsized dimension images). I've tried fudging the dimensions up and down and each time Facebook crops the images seemingly arbitrarily. I've tried uploading in JPG and PNG. Same issue each time. First time this has ever happened and NO CLUE what to do, very annoyed, have to get image up to promote a Sunday event. Please help!
Oh yes, using 72 dpi...

[dan p]

they have a crop feature for having cover photos. if you tried resizing it multiple times, using trial and error, but have not got the pic to fit; wont be able to tell you much more than that. trial and error. resolution doesnt matter much, it will automatically convert it to its own filesize.