If you can save documents as "Save As" check that the last image/s downloaded appear as thumbprint tiles (not blank tiles) in the "Save As" window.
What I discovered, is that if you change a document image reference number to a title, to find it easily on the pc search later, it will sometimes download blank. Also download to one file, they are easier to find, rename and move to where you want later.
If you find an important, but difficult to find image (or document in an archive, or archive catalogue reference) accidentally, it pays to back-up details in a Bound Notebook, or have a ring binder folder, for that purpose, because you never know when a Hard drive might fail either! Or your power supply goes off during a large update and your pc battery goes flat.
I've found items in the British Newspaper Archive, but because the OCR is poor for some editions/ dates, it can take some time, or be impossible to find it again later, so always worth taking notes.
Mark