Whilst cutting another new part I used 'feedhold' to stop the machine just to check something was not going to collide. Then I hit 'start' but instead of continuing on a +X direction to the end of the cut the machine moved in +Y. It was about 8mm into a profile cut so snapped the cutter.

Luckily this was in the scrap part of the material so no harm done. I changed the bit, homed, ran it all again. Later on in the same profile cut (in the -X direction this time) it was almost to the bottom when I pressed 'feedhold' again to check one of the clamps was not going to get machined through. When I hit 'start' is again went in the +Y direction. Luckily I had my hand over the e-stop but it still took a chunk out of the part!

I've never had this happen before and haven't changed anything in software, just the Z axis bearing change. Any ideas?