@Solla-topee unfortunately that did not work

  @PaulieX 

Same thing, noticed with my C120 v1.0. Don't think i've heard it before, since 1.3.1. it's extremely loud and at night, i figure it must drive the neighbours nuts!

I think 1.3.1 changed wifi chip/firmware/drivers or something, because my C120s were working (essentially) flawlessly before, perhaps right on the border of my WiFi signal though. However since the update I've had them drop out reporting "Offline" in the app and combined with the loud announcement "connecting to wifi.... WIFI connected1" at other random times as PaulieX noted above.

 I've reset and reconfigured both cameras but that didn't resolve it. I've brought one camera which has been more troublesome closer to the wifi AP and issue has disappeared, so it looks like i've lost some range and will need to look at extending the wifi signal closer to where the cameras are.

All that said, i wonder if TP-link rep could confirm - is the camera supposed to enter setup mode if it can't maintain a good wifi signal with the configured SSID/AP?

  @tecnika 

Yeah that's what I think that it's an update problem just it was working/ not shouting at me before.
 I've had a reply from Support and they are going to push a firmware update. I will keep you informed in if fixes the problem.