Microsoft has added a new feature in Windows 10 that automatically sets your default printer to the last one used. That means that if you print labels on a label printer and full sized documents to a regular office printer, the default will keep switching, potentially causing a disruption as reports attempt to print on the label printer, etc.
There is a setting to disable this behavior:

Open Settings, then go into Devices > Printers and Scanners
Set "Let Windows manage my default printer" to Off