Starting below model top and dont know why

Hello All, im using X-50 with Fusion 360. My problem is my bit on the z axis starts over a 1/4 inch below where it should. It should start at or slightly above my model top. Unortunelty, it does not and I hit the panic button.

I manually position and then zero x and y. I use the probe for Z. Any ideas why im dipping below the model hieght when i start the job?

When you do a bit change do you have to change the setup also? am i suppsed to change the setup from stock box to model? since ive already faced off the top? Does the model top option in the tool tab override the stock box option in the setup tab?

Also it looks right in Fusion - CAM - simulation

Thank you all.

Sounds like a difference between where you defined the z origin in setup and where you are probing. If you define the z origin somewhere on the stock top and then face off the top, then you lost your ability to rezero to the stock top. In that case you should define the z origin in setup to the stock bottom then whatever machining you do to the top you still can rezero to the stock bottom.