OH man, had the same problem myself, crashed once because of it. Right after the program started the first thing it did was head for the table and bury my 1/2 roughing mill up into the holder. Luckily I hadn't set the setscrew into the flat because it was a test run...just in case. Also ran at 25% feed and rapid.
I put a z5.0 after the G43 in my post per the advice of the guys on the Onecnc board. My machine was going rapid to z0 before putting the height offset into effect. That worked fine. At least untill I use a 6" tool. I should change it to z10.0 now that I think about it.