I’ve read the support page about the differences between roles “viewer” and “viewer-restricted”.
One information is not communicated. Viewer-restricted members cannot share their drafts.
This info cost quite some time of my team yesterday (and time for the support team).
It would be great if viewer-restricted members kept the capabilities of sharing their files - and also, the already shared files should continue to be available. But if nothing can change, please add this info in your documentation pages.