I got a Syncro Saw for Christmas from my dad when I was about 10 years old, I still have it and it still works {sort of} but it was from my Dad so it won't be going away until I do. I'm only 84 so it will be a while LOL!
it's possible that one of the wires to the switch s loose. Try taking it apart and see wha is loose in there. When pushing down on the arm you might be causing it to make contact and run.It's probably an easy repair. Try bypassing the switch to see if it's possibly a bad switch. Just because it is a new one it doesn't mean it is a good one??
John is correct with his post. You might clean it up by making one more pass with your router set just a fraction deeper and don't move too slow as John said the second pass might clean it up and the depth won't be enough to really show if you keep it small enough.
It does appear that your bit could be dull they don't last forever. If you have any diamond cards you might give the flat sides a little touch up before proceeding.
TransTint wood dye works really for staining wood without raising the grain, Not cheap , but it works great; Rockler has it, as well as other woodworking suppliers.
I sharpen mine with my Makita wet sharpener, it does a fantastic job. Not a cheap tool but well worth it to have in the wood shop for things with an edge. I have been using it for about eight years now and I would find it hard to do without.
They are usually always available and they have other brands as well if you want DeWalt they have them also. You need to go to their website to investigate