My Gallery thumbnailing on File upload/link broken

Thumbnailing a file (either uploaded or linked) used to work, now it does not. Simply put - when I try to either upload a new thumb, or link to a thumb, and hit "Update" (or Save on the back-end), the browser window acts like it is processing, and then proceeds to show me a completely white/blank screen.

I attempted to work with this on the front end a little bit, and now I am no longer presented with the option to modify the thumbnail on any file inside the Album. Files that have existing thumbnails aren't able to have those thumbnails modified - the option when editing the item no longer exists in the UI.

When attempting to remove them so I could re-add them, the response from the front end I received was: "414 - Request-URI Too Large - The request URL is over the maximum size allowed!"

I am wondering if this had something to do with the thumbnail update failing. Note: I am using Chrome v80.0.3987.149 (Official Build) (64-bit)

Seams to be working fine locally in my tests and on our demo site. Please ensure your install is completely up to date. Are you trying to upload a large thumbnail? The thumbnail input doesn't support client side resizing so that could be a potential issue.

When attempting to remove them so I could re-add them, the response from the front end I received was: "414 - Request-URI Too Large - The request URL is over the maximum size allowed!"

That means the form URL was too long somehow. It's possible the return URL is causing the form URL to be too long, but I don't see how that could be the case. Where are you managing your gallery from? For example from your Gallery profile tab? Do you get this same error even in backend?

As of the time of error reporting, all core and plugin files were up to date. We just released the website today, and were in development mode over the last month - I check the CB code quite often for updates.

The thumbnail I was attempting to place on a file was only ~28KB in size, well under thumbnail limits. And I verified it wasn't corrupted in any way by opening/re-saving in multiple image editors.

I was attempting to manage the file inside the album both from the front-end and the back-end using a SU account. Both experienced the same issues with a blank screen and no thumbnail update.

As a sidenote: this may be related to the problem I just reported about the blue Download button on files not working when they are 'linked' files - it only works for us when the files are uploaded using CB Gallery. I haven't re-tested since I switched from linking the files to uploading them. I will make a new hidden test album this weekend and see if thumbnailing on uploaded files works.

Retested adding thumbnails to linked files and is also working fine in my tests. Recommend checking your server error log after triggering your issue to see if there's any fatal errors around the time you attempt to attach a thumbnail. If issue persists please PM backend super administrator login credentials with steps to reproduce and will take a look.