rndc flush with shared caches does not affect all ADBs
When flushing a cache using rndc flush the view flushes both the cache and the ADB (among other things).
When using a shared cache the cache may be flushed by specifying any of the view names attached to it. When this is done only the ADB for that view is also flushed. All other ADBs using data derived from the cache are not flushed.
This may lead to a situation where the resolver is using prior ADB data for recursion that does not match the data currently in the cache.
The operator may work around this by issuing a flush command without a view name, but this may be undesirable if they have other views that aren't attached to that same cache.
Ideally flushing a shared cache should imply the flushing of the ADBs of all views using that cache.