I had to think about that, but here is a simple test. Unfortunately, it still takes a bit to explain.
On a system with the TV Show "The Flash" in the Library, identified correctly as the 2014 series rather than the 1990 series, you should have a Series Cover Art image called "The Flash (2014).jpg" in the "Cover Art\Series" directory. The series is identified as "The Flash (2014)" on TheTVDB, although
I just called it "The Flash" in my test Library, with the correct value of [TheTVDB Series ID] saved, which is 279121.
If you also had the original 1990 series called "The Flash" (TheTVDB ID 78650) either now or at some stage in the past, and still had the image file in the "Cover Art\Series" directory, it would be called "The Flash.jpg".
Regardless of the way the Cover Art Series directory is sorted in Windows, MC looks it up by file name. So "The Flash (2014).jpg" is listed before "The Flash.jpg"
First sign of the issue:As I have renamed the "The Flash (2014)" series in my test Library to "The Flash", MC should be using the Cover Art image file "The Flash.jpg", if it uses an exact match. It doesn't however. It uses the first listed file, "The Flash (2014).jpg".
Second sign of the issue:If I view the series in Standard View with the top pane's List Style set to Thumbnails, the "The Flash (2014).jpg" image is used as the series Cover Art.
If I rename the image file "The Flash.jpg" to "The Flash (1990).jpg", that file is now listed first in the file list.
If I then refresh the View above, the Cover Art image changes to the "The Flash (1990).jpg" file.
If I rename the "The Flash (1990).jpg" file back to "The Flash.jpg" and refresh the View, the Cover Art image changes back to the "The Flash (2014).jpg" file.
Third sign of the issue:With the two Cover Art images, "The Flash (2014).jpg" and "The Flash (1990).jpg" in place in the Cover Art Series directory, the latter being used at that time as above, I ran the "Get from internet" function.
MC used the [TheTVDB Series ID] field to look up the correct series, The Flash (2014), on TheTVDB. I selected a new Series Cover Art image and saved it.
MC correctly saved the file as "The Flash.jpg", because the Series is called "The Flash" in my Library, However, MC didn't use this new image. It continued to use the first listed file, in this case "The Flash (1990).jpg".
The three tests above show that MC is using the first Cover Art image file listed in the Cover Art Series directory with a partial name match, rather than the file with an exact match. I expected it to use an exact match to the [Series] name before Ashfall raised this issue. It does explain some of the strange results I have seen with my Doctor Who collection though.
It also makes the
Wiki wrong as it says the file naming is [Cover Art]\Series\[Series name].jpg, which makes me think this functionality has changed as some stage.
I have attached a copy of the original Series Cover Art files I used in case that makes it easier to test or understand what I wrote.