What is in the Author field besides the Authors name (ASCII preferred)?
Without a proper Author (or ISBN), the chances of getting a correct
set of metadata is less.
Each source can be fine tuned to which OTHER fields should be considered.
Note the ticks on the (red line) apply to ALL
Select a source (blue circle) and click the red circled button to set each selected source.
FWIW the numbers allow you to choose preferred cover source priority.