Wireless isolation - but not sure why

I have a strange issue that I believe just started. I have a wireless printer and suddenly I cannot ping or print to it from WIRELESS clients on my network.

I have multiple wireless devices I'm testing connectivity to the printer from. All three devices are using the same 2.4 GHz SSID.

From a WIRED client, it can ping the printer just fine and I can print to it.

My initial thought was that I turned on wireless isolation, but that's not the case. The setting is un-checked. For fun I checked it, Saved and Applied the setting... and a minute later un-checked it and re Saved and applied the setting (all from LuCI).

Any ideas where I can look to troubleshoot further?

WRT1900ACv1 Running Lede Reboot SNAPSHOT r4651 - Davidc502 build.
Wifi Driver: 4.4.79+


This looks similar to this issue:

Isolate wireless clients? and to Clients in same WLAN can't reach each other.

It's also mentioned in a bug here: https://bugs.lede-project.org/index.php?do=details&task_id=272&opened=74&status[0]=

It looks like a known issue.