In a perfect world, it would.
But there are an awful lot of variables with this, and it can be caused by anything from a dirty lens (it really is one of the top culprits 
) to a slight amount of warp in the material, or a bad spot or knot in the wood. So the folks at support have to be kind of general with the suggestions to make sure that everything has been checked and eliminated.
What I always check for if I get incomplete cuts is:
- Is there even a tiny amount of warp in the wood?
Using the Honeycomb Pins has been a lifesaver for me because the wood down here always warps. (High humidity area here.)
I keep a little spice jar of them next to the machine and use them up front…no more problems with incomplete cuts.
If there is one side of the bed that consistently doesn’t cut through, but the rest is cutting okay, that’s a sign of a slight warp in the material. It doesn’t take much to cause an incomplete cut.
- The lens needs to be cleaned using the instructions here:
https://glowforge.com/support/topic/cleaning-service-and-moving/cleaning
That needs to happen more frequently depending on what you are using the machine for - engraving on things like draftboard and plywood throw up more resinous gunk than etching slate, and cutting throws up more gunk than engraving. When the tube starts to look a little yellow, i usually clean the interior, but it’s usually only every few weeks.
- The part that I mentioned above about adjusting the speed for the design is not something that Glowforge can suggest, since they don’t know what kinds of designs we’re trying to cut. And that comes from personal experience after years of designing digital cutter files - we had to make special allowances for tight curves and corners in those, due to the limitations of the machine movement. It translates very well into laser work as well.
Once you know it though, it’s a lot easier to modify your settings slightly and you’ll get even fewer bad jobs.
Having done those three things, if you still have trouble cutting through the Proofgrade consistently, it might be a focal issue or a power issue on the machine, and you would need to open a support ticket on it. (I’m not talking about just a little tab or two not cutting through, I’m talking about it’s not making it all the way through on any cuts.)
As you get a little more comfortable with the materials, it will happen less and less. I can’t remember the last time I had an incomplete cut on anything. 