12.1 Listener disappeared after patch applied

I needed to apply 1-off patch 20636003 on 12.1.0.2 running on a development AIX 7.1.4 box. As per instructions, I shutdown all apps running on the $OH, which happened to be just 1 DB and the Listener. Since I have 11.2 DBs on this box, I fired up an 11.2 Listener during the patch.

Patch applied, 11.2 Listener shutdown, 12.1 Listener started up, 12.1 DB started up, and all's well. Until two hours later when I get a call that they can't connect to any DB on that server. I login and there's no Listener. No dumps or incidents in ADR -- it's just gone. The listener.log (and log.xml) just stopped after the last connection, with no errors.

With no logging to troubleshoot, I shut down the 12.1 DB, and did a "relink all". I verified the new binaries were created and started the Listener and the database, and they've been fine since (16 hours and counting). I see that there are 2 Oracle libraries that the tnslsnr binary is linked to. One, libons.so, was not touched since the original install, and the other, libttsh12.so, was updated after my relink, so I don't know if the patch touched it or not.

I don't recall ever seeing any Oracle program just disappear without leaving a trail before (since v7 anyway). One anomaly here is that Support told me to use the patch for 12.1.0.2.160419 even though I'm on 12.1.0.2.170814.

Anyone ever have their Listener disappear before?

TIA,
Rich

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