I use FD 2/0 and they are easy on breaking.
sometimes I think that on dozen of blades have the tendency of breaking easier then the other, maybe it's the hardening process that makes them so hard that they break more often....
just using the quick-release-clamp on my hegner will break them.....
so I'm very careful with the strain on the blade, always use the tension knob.
and like raymond said, heat could be the second problem, so slow is better.
but the FD 2/0 makes really nice cuts, I don't use them a lot, but on small scroll and fretwork it is sure worth the extra effort.