It seems to me, that kirby’s thumb-generation not always uses the previous generated thumbs in thumbs-folder.
I have a website which uses intensively thumb-generation (resize, crop, quality). Although all thumbs exists, kirby generates them again. But the file-timestamps of the previous generated thumbs are unchanged.
Maybe kirby does not always identify previous generated thumbs and then tries to generate them again, and on save of these newly generated thumbs it doesn’t overwrite the existing ones.
No, the behaviour is completely different. The files are kept in the folder, and are not deleted. There is no manipulation of the page in the panel, so kirby would delete the thumbs. Eg. when I open the page one day, the thumbs are generated/used. Next day, where meanwhile nothing changed, when I open the same page the thumbs are internally again generate, although the thumb-files exists, but not updated on files system - and the files should not be updated.
Edit: This doesn’t concern to all images/thumbs. This effect occurs random. Maybe it depends on PHP internal cache management?!
I guess you could just put in a dump() command in the source code or log something to file to see if the isThere() check is true and the thumb newly created. I can’t really believe that the thumb is just overwritten without the time stamp being modified. Even if I set the overwrite option to true, so that the thumb is always recreated, the modified timestamp gets changed.
I don’t think it works like that, the thumb method does not return an object of type Thumb, but of type Media. What I meant was to dump something directly in the thumb constructor in the source code (in kirby/vendor/getkirby/toolkit/lib/thumb.php)