orbi rbr860 firmware 7.2.8.5 img file is missing from Dec 2025 security release update file

I am running a 3 node orbi system. (rtr + 2 x satellites). The solution is running 7.2.8.2_5.1.18.

I am actually struggling with domain.local issues, but in looking for a fix, I noted a security release for orbi rbr860 so I downloaded it from the support site.

Having unzipped it, I noted there were only 2 files in the zip, which I thought was odd. (release notes and .chk file). I tried uploading the .chk file to the satellites to see what would happen and it failed as I expected. The error msg returned was "file not found  (*.img)", so I assume its looking for an img file, which is not in the file from the netgear download centre. 

Where do I get a complete version of the update and also, why does Orbi firmware auto update not update to this new security release version?

Thanks

-Anthony