Storyline 360: 360° Images Stuck Loading — Is Anyone Else Experiencing This?

Adding a data point for the support case: multiple people hitting this on different images and file sizes, with the August build working, points at a regression in the current build rather than your project files. If you haven't already, file a support case with a minimal project containing one 360° image — the more reports tied to the same build, the faster it gets triaged. And if you revert to the August build as Carl suggested, test one 360° image first before committing a whole project to the older build.