In the last six months, 23 Phab tasks were created for a multimediaviewer-thumbnail-error due to the code in resources/mmv/ui/mmv.ui.canvas.js.
What happens in those task is that usually
- @Ramsey-WMF moves the task from Untriaged to Needs Reproduction on the Multimedia board, and
- @AKlapper adds a stock answer ("When you click on the first link directly, can you access the image and is the image displayed in your web browser? If it is not displayed, what is displayed / which exact error message is shown? Does this problem also happen with another browser (which browser)? Have you tried to bypass your browser cache?")
Looking at those 23 reports, apart from
- server-side broken wiki setup/configuration issues like in https://phabricator.wikimedia.org/T177811 and https://phabricator.wikimedia.org/T188178
- client-side browser add-ons/extension issues like in https://phabricator.wikimedia.org/T178358
- client-side broken antivirus software like in https://phabricator.wikimedia.org/T180661
- PEBKAC stuff like trying to access non-existing images like in https://phabricator.wikimedia.org/T185432
, all other reports never received a followup from the original reporter.
This does not look like a good use of triagers' time, MediaViewer maintainers' time, and of a task tracker software in general.
Consider pointing users to a wiki page instead which covers the cases listed above and how to perform initial debugging. Then on that yet to create wiki page at the very end if none of all that helped, offer a link to report the issue to Wikimedia Phabricator.