If anyone is still having the following issues:
- scrubber, reply composer, sticky or other discussion features do not work on some discussions
- auto-images (via fof/formatting or similar) are displayed too small
Please make sure that you have version 0.2-beta installed by running
composer show squeevee/flarum-ext-fancybox
If you find you have 0.1-beta installed, I think
composer require squeevee/flarum-ext-fancybox:@beta
should do the trick.