Updating bookmarks with policies appears to be broken

We've been revisiting updating bookmarks via Desktop policies and it appears that in 8.5.1 it is (still?) broken.

When the policy is initially applied some users get the bookmark, some do not. We have tried the debugging steps outlined in IBM's Troubleshooting policies and settings document. These steps sometimes work but more often than not don't.

Interestingly in the 8.5.1 contacts database an number of the agents that the technote tells you to run no longer exist.

Another interesting feature is that if a user gets a bookmark icon added, and then they deleted it, there appears to be no way to add it back via a policy.

Has anyone actually got bookmarks and policies working together nicely ? If you could point me in the right direction I'd greatly appreciate it.