Thumbnail generation fresh install some files missing thumbnails

Hello, I have the latest install of NC on ubuntu with Mariadb. Pregeneration completed of thumbnails. Some images seemingly random, didn’t generate a preview. I went back to the config.php and added a line ‘preview_max_filesize_image’ => 500,

files:scan followed by preview:generate–all didn’t update the files with missing thumbs. OK…so then I opened nextcloud file explorer, searched for the file names, found them. They still don’t have a thumbnail, but they open up. Expectation was that the thumbnail would generate upon the search, but it did not.

What are some other possible solutions, I have already removed/added the pictures app, cleared cache (deleted the data folder and all contents/deleted all users and user data) rebuilt and rescanned and re indexed. Files still look the same. In windows, those files have a thumbnail, no corruption.

Any ideas? config.php was the only file I changed to allow these files to load. The file is actually only 30 mb in size and is in a batch of images of similar size , some of which load some don’t. Then I found some random non large images that also didn’t load, but in the same batch other images worked.

Is this a database issue where it has the wrong file to look for…or what.

preview_max_memory comes to mind as a possible culprit.[1]

There may be some other clues in your Nextcloud Server logs (particularly with loglevel 0 temporarily set), though some preview generation errors aren’t logged under normal conditions because image processing is notoriously easy to trigger failures with (consider that in a large batch of images, particularly from a bunch of difference sources, chances are that some images will be corrupt or have non-compliant formats).

Also note that pre-generating previews may not be so important anymore, since concurrency support was added in… I think it was late in the NC26 cycle.[2]

What backend are you using for preview generation?[3]

[1] Configuration Parameters — Nextcloud latest Administration Manual latest documentation
[2] Configuration Parameters — Nextcloud latest Administration Manual latest documentation
[3] Server tuning — Nextcloud latest Administration Manual latest documentation

I had the max image size already set, but it didn’t work. I tried a few other additional items. Here’s a copy of my config for those who have trouble in the future…

'preview_max_filesize_image' => -1,
'preview_max_memory' => -1,
'preview_concurrency_all' => 12,
'preview_concurrency_new' => 8,

followed by a files:scan and generate:preview-all -vvv.

After these additional changes to /var/www/html/nextcloud/config/config.php both large thumbs and almost all broken thumbs worked. Setting to -1 made them load actually.