I’ve run into the same issue w/any file over 4MB, had to resize/shrink my docs to 3MB or less to get them to upload reliably….
Just make sure they’re still legible when you downsize them, been rejected before for “blurry” PDF docs….
I’ll second the Mag-Lula as well - I do have those & they’re great, but I automatically associated to a “stripper clip loader”, although they’re easy enuf on your hands.