Not sounding right at all. I'm going to put out 2 rather simple questions that aren't meant to be offensive.
1.Have you changed the configuration for the mill to run the passive probe by running the configuration utility?
2. Do you have your passive probe loaded in your tooling table with the correct probe tip effective diameter plugged in? I put mine in as tool number 99 and I don't have any length offsets programmed. Before I probe I manually change the tool to T99. If you choose let's just say T2 with an odd length offset and try to run your probe it will sometimes default to motions like you are seeing.
3. Check on what philbobb had alluded too.

Good luck!