Couple points to add: 1) - Don't assume that a certain brand and type of material will not change properties over time and or different lots. 2) Make sure, when troubleshooting, that you are using models that will help with specific problems, ie: temp towers for temp issues, single layer discs for first layer issues, 10mm cubes for layer adhesion, dimensional issues and extruding issues, etc. Usually these test prints are quick, and allow you to focus (and eliminate) fewer issues at a time.