Hi, this is Driller from Drillimation Systems.
There were reports of a bug in the WordPress block system where HTML code in the Gallery block was displayed instead of actual images. Drillimation Systems notified WordPress about the issue and they are currently in the process of crushing the bug. We have no date on when this update will be rolled out.
This is a developing story and this article is certain to change. Make sure you stay updated. Have a good day!