Microsoft recently pushed out an update to Windows 10 which allows Windows to manage the default printer (sets it to the last printer used). If you do not want the last printer that you used to be the default printer, you can turn off this feature (which is the way that Windows used to handle the default printer).

Go to the "Printers & scanners" window and change the "Let Windows manage my default printer" switch from "On" to "Off".


Remember, the "Printers & scanners" window only gives you the most basic configuration options. If you need to make detailed changes, you need to go to "Devices and printers" in Devices, Settings, or just search for "Devices and printers".