I am having the same problem since the upgrade.
Here’s an excerpt from my settings.
I have watch on dig set for one of them and every few minutes it fails to resolve. Then, after a few minutes, it resolves correctly again for a while.
Below is an excerpt of a packet trace.
You will notice that the query that succeeds is an IPv4 query, while the one that fails is an IPv6 query.
I am not sure what has changed, yet. I have not made changes to my host (Ubuntu 19.10), but an update may have.
It seems, however, that Unbound does not respond correctly to the AAAA request and instead of returning what is in the hosts settings, it returns the results from the authoritative nameserver on the internet.