When I reported this the bug/feature was changed but I noticed a while
back (late 8.x maybe 9.0) that it is back. So if the purp can get you to
the wrong server only once it may be possible to keep you there.
It was actually fixed in 9.2.3rc1.
1429. [bug] Prevent the cache getting locked to old servers.
Of course I still don't think its a bug, and it forced people to remember
to actually finish the job when they moved their DNS around. But whatever,
its easier than doing a rndc flushname name (which finally got put in).