Never seen cascading work either. Just ends up in endless wasted time formulating 5th level deep okrs, that become so specific they are quickly irrelevant as the organization changes and pivots over the year.
No one should be writing OKRs that deep. If your organization has five levels, the fifth level should be writing their own top level OKRs. They don’t take that long unless the company is critically indecisive. They’re for companies that are capable of executing and need to focus or change directions.