I recently purchased a Kreg Precision Miter Gauge System for my table saw. I assembled everything and calibrated it per the instructions. It has been working great doing crosscuts. I had my first opportunity to use it to do miter cuts since I'm making a picture frame.
Each outside edge of the frame is 19 1/4" long. So, I rough cut 4 pieces 21" long. I then set my Kreg Miter Gauge to cut the first 45 degree angle. I placed the outside edge of a frame piece against the gauge fence and made the first angled cut. Then to cut the 45 degree cut on the other end I flipped the piece, keeping the outside edge against the gauge fence. Then using the scale on the top of the miter gauge I set the Swing Stop to 19 1/4". I then cut the second 45 degree angle.
Here is the problem - after cutting both ends of the piece, when I measured the outside edge of the frame it was 9/16" too long!
So, did I do something wrong or can you not use the scale on the guide when cutting angles?
My first guess is that the flip stop isn't wide enough to properly register the stock. Did it stop at the extreme end of the point, or somewhere down on the angle?
Second guess would be that you set the stop with the guage at the 45 position to the closest point on the blade. Set the flip with the guage in the 90 position.
If you set the gauge relative to the blade at 90, then move it to 45, the end of the gauge is going to move further away from the blade as it pivots resulting in a longer than desired cut.
The answer to your question is yes. After spending a few years in a machine shop, and many years remodeling houses, I've found that a good rule of thumb is if you move anything, recheck for accuracy. Unfortunately, pretty much all of my mistakes were caused by my lack of diligence. You are lucky, though, that you ended up long. My rather large pile of "on hand stock" is a result of my luck going the other way. Be patient...take your time...and above all, keep trying. Making stuff is very self satisfying. It's the pros that make it look easy. They weren't always pro, either, ya know.