[SOLVED] Issue with Default+ Thumbnails

[Mattt]

I have Band/Artist logos in the parent folders in my music collection so thought I would try the Default+ setting.
The logos now show up when in folder view.
But, in album view many of the album covers are at a lower resolution than before changing this setting. Some are so grainy the writing is unreadable; they definitely were not like this before.
I still have resolution set to 600px, and cover search priority set to embedded as before the change.
I've regenerated twice and tried restarting etc.
Any ideas on why this would occur and how to fix it?
Cheers

[DRONE7]

Regenerate both the library and thumbnails/covers and clear your browser cache ?

[Tim Curtis]

Do the albums that exhibit the issue also have cover image files in the album folder?

[Mattt]

Do the albums that exhibit the issue also have cover image files in the album folder?

Yes, but so do the folders that don't have the issue.

[Tim Curtis]

The help for the Plus options

Plus: The + option adds image types jpg/jpeg, png, tif/tiff to the scan which enables thumbnails to be generated for images in parent folders of the Album folder for example Artist or CD box set images.
Note that incorrect thumbnails may appear in the Library if the Album folder also contains image files and "Cover search priority" is set to Embedded.

[Mattt]

Changing the setting to cover file has fixed the resolution issue