(Editorial comment: Hey Intel mods, light a fire somewhere to get this driver put up on your own website.)
Let's try this first, to try to get on the same troubleshooting page.
Download this driver: https://www.crc.id.au/files/Intel%20AC-7260%20v17.12.0.4.exe
It is version 17.12 that another member downloaded from an OEM site. This is a self-extracting zip file that includes the drivers for the various Windows flavors.
Once downloaded, run it to extract the folders for the versions of Windows.
Go to Control Panel and uninstall ProSet software. Let Windows run your wireless. Restart.
In Device Manager, click open the adapter properties and then click to update the driver. Point Windows to the extracted folder on the PC for the downloaded driver. Let it update.
The adapter will reset. See what happens. Then, list all of the settings of the driver in the Advanced tab. List them here so we can compare what the defaults are in the driver with what I've got with my working card. Bit of a pain, but we need to look at them. Also, what shows in the Power Mgt. tab?
We should also look at router settings. List them for both bands of the router your connecting to as we work on this.