Used white and brown chipboard. I use BB plywood normally, but recently the quality of BB has dropped dramatically. I had to switch to chipboard for consistency and it looks like I will stick with it going forward. Its bad out there with anything to do with plywood or lumber!
If you like the idea of switching to a consistent paper product, check out matboard. It cuts consistently and comes in as many colors as you can imagine.
Its called chipboard but its mostly high density cardboard/fiber, no visible pieces of wood in it. I tore into one to sort of delaminated it. Didn’t see any voids or pieces of cardboard or wood. It looked very consistent, more like draft board, without the crumbling powder.
I use a bunch of chipboard in “plain”, white, and black. It comes in different thicknesses although I’ve generally only used what is sold as “medium.” Great stuff, cuts very fine details consistently. If char is a problem, I toss it in a bag of salt that I keep alongside the machine. Doesn’t completely remove it, but it helps. I have a dozen or more things around the house cut from it, and have given dozens more away to friends and my daughter. It’s what in my experience Jigsaw puzzles are stamped out of, and I’ve made a fair few of those as well. I laminate pictures/photos/commercial product boxes onto a sheet, and cut from that. One of my favorite materials.