In this thread, @_az and @mnordhoff investigated a perplexing problem someone was having with SERVFAILs. @_az not only diagnosed the specific problem, but put together a detailed bug report for Unbound. As of today, the Unbound maintainer (Wouter Wijngaards) has confirmed the issue and patched it.
https://nlnetlabs.nl/pipermail/unbound-users/2019-February/011349.html
Great work @_az, thanks so much for working on this!