Personally, I have not experienced this, however, I appreciate all installs are different. Looking at your video it seems you have a fair few plugins which could always be the cause of conflicts.
Have you tried disabling all plugins and then running the CSS loading? (on a staging site if its live). At least that way if it does work after doing so then you know the culprit is a plugin and where to find the source of the issue.
Then you can activate them one by one and run the CSS loader until you active the one that breaks it.
If however you do disable all the plugins and it still does not work, then that will surely be one for the dev team i would imagine.
please send an email with login credentials, a short description of your problem and a link to this thread to help@bricksbuilder.io, so one of our developers can look into it.
Just wanted to give an update, it seems they have found the issue, and it will be included in the final 1.3.7 release! Thanks for all the work Bricks team!