That makes sense. Guess it will take some experimenting to see what an acceptable range is as far as the machines ability to push through a given material.
Last night I tightened the X axis belt and shortened the depth and increased the stepover. Don’t remember the exact values…I think it was something like 0.07 inch depth and 0.07 inch stepover with a modified feedrate. The machine no longer missed steps and maintained the path correctly. The finish was not what I was looking for so will need to adjust the stepover some to get a smoother look. My assumption at this point is that the belt system just couldn’t push through the material without missing. It may have even been stretching the belt which led to slipping and the eventual missteps.
I modified the Fusion360 toothpath last night to use the following settings which I’ll try tonight to see how it does: 16,000 rpm, 161 in/min feedrate, 0.03 inch depth, 0.03 inch stepover. That gives a 0.0034 inch chip load and hopefully a much smoother finish. This is with the same bit. Will take a run and report back how it did 
On another note, while playing with variables in the feed/speed calculator I noticed the previous settings I was using were resulting in cutting forces greater than 5 lbs (according to the calculator) which seems like a lot. The settings above have a cutting force of 0.83 lbs so hopefully that won’t overload this machine.