What kind of CNC machine are you using to do this? The feedrate seems slow, if anything, and the depth of cut seems conservative enough. I'd suspect the machine is not rigid enough, but you say another type of bit works okay. Is the Amana tool solid carbide while the Bosch is High Speed Steel? The former is more brittle, but it still shouldn't be breaking that much. Have you tried an up-cut bit? Usually down-cut bits are used when cutting plywood, so as not to disrupt the top veneer, but it sounds like you're cutting solid wood. I don't think the coating's really necessary either.