The last few projects that I’ve cut out have been leaving a groove at the bottom. I clamped the boards down well, and it’s a new 1/8" spectre downcut bit.
Most of the wood I cut is 1/2" thick. It’s really exhausting having to sand that lip down on every edge of every piece lately. Just curious, the pocket on this project also left pass marks. Could that also have to deal with the same problem?
There could be many reasons but here’s a couple things that may help. Reduce your step-over percentage under machine settings, especially on the last pass. You could do the whole carve as normal, then change your step-over to 10-20% and set your depth to the entire depth of the carve or even .002" deeper. Also an up-cut bit or a straight bit will leave a flatter bottom, but the trade off is you might have a little tear out at the top.
Another good tool for dealing with those marks would be a sanding mop. It attaches to your drill. Look up the Sand Fly sanding mop or there are others.
I hope you get it figured out, Happy Carving ! 
