A Microsoft file hosting and synchronization service.
There is this story of ongoing account migrations floating around as the reason behind the shared-folder bug. As some forums have already pointed out, this platform-migration is not the only issue behind the bug. The new platform has some bugs and it is partly incompatible with the old one. Those bugs have not been discovered by the OneDrive team's integration tests, but by the author of an independent Linux OneDrive client. Have a look at the ongoing development and discussion:
https://github.com/OneDrive/onedrive-api-docs/issues/1890
TL;DR
The OneDrive team does not even seem to be aware of the issues. Everyone should be prepared for a long wait!