This fix aims to solve the problem when only some individual images go missing, seemingly randomly. You might notice that unloadable images get popped from the grid. You can stop this error checking and find the cause of the problem by following these steps:
- Edit your shortcode and set General tab > Behavior of the plugin > Error checking to No - this will show the empty spaces.
- Right click on a missing thumbnail and choose Inspect. (Chrome, Firefox)
- Find the img tag and observe the thumbnail URL in it - might as well just open it on a new tab to see if there are any server errors.
Check the following:
- Special characters in the file name. It's generally not advised to use anything other than alphanumeric characters and dashes, underscores. Keep filenames short and simple, absent spaces, accented characters and symbols.
- The image is missing from the server. The thumbnails are created from the Large sized images, which have to exist first. Right click on the thumbnail and try to open its target on a new tab, instead of the lightbox. If the target image is missing, then please re-upload it.
- The image is missing in the desired size. The Lightboxes tab > Maximum size for lightbox setting controls which image is selected for lightbox display and consequently as a source for thumbnail creation. It could be that you've chosen a WordPress image size that doesn't exist for that image (because the image size was defined later than the image got uploaded). This is common after switching themes or defining custom image sizes in the functions.php file. Use the Force Regenerate Thumbnails plugin to handle missing image sizes.
- The image is missing from the 3rd party image source or a CDN. It's not unheard of to have an image go completely AWOL, even from Facebook albums. In case you manage the CDN, use their tools to make sure all images and thumbnails are hosted there properly.
- Error in uploaded images. It could be that your Media Library or NextGEN Gallery has corrupted image uploads. A telltale sign is when you try to edit an image, the page shows much less information and even a missing image. Also, if you were having difficulties uploading image lately, check them. Can they be inserted into the post on their own, without JIG?
- When using cheap shared grid hosting, the server may be overloaded and not able to handle your request at creating or serving the thumbnails. Also, loading a large number of thumbnails at once makes this even more likely. The solution is to use a CDN or at least the free CloudFlare. Sometimes hosts even block your access as they mistake you for an attacker, due to the large number of requests. This is especially true for GoDaddy hosting which should be avoided.
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