The problem is I want to turn off SIP ALG as they frequently cause issues with various PBX's and VoIP SIP phones.

Seeing the following in the logs would suggest it is turned on by default - nothing in configuration pages to disable it.

10	Jun 24 08:42:32	OTHER	INFO	System Initialize Finished.
9	Jun 24 08:42:13	SECURITY	INFO	SIP ALG enabled

Some other TP-Link products can resolve this issue via telnet, telnet on here is closed.
Interestingly, why is port 49152 open from this device?

Sorry, I thought the posts were clear:

Yes the WA801ND is in AP mode.
The firmware is the latest stable available on site as of yesterday.
The startup log (shown in previous post) shows that the problem is caused by the WA801ND

Wireless SIP devices connect via wireless to the WA801ND. *CURRENTLY* this is not causing any known issues with my current setup and equipment, however from experience SIP ALG implementation causes problems with MANY SIP devices, an option to disable it so that packets can traverse unaltered would be a perfect solution to prevent issues.

I am assuming that since the AP tells me it's using SIP ALG (enabled) that it really is!

Thanks
Steve