When I try to get 1.5” contour cut on some projects, if I set the bit long enough to make the cut, it crushes into my bit setter and I get a “probe is in an unexpected position” error.
First is the bit long enough to cut 1.5" depth. Secondly if you have a bit that can cut 1.5" deep how deep in the collet is the router bit. The bit should be at least at the top of the collet to get the maximum grip on a bit. Using a bit that does not have a 1.5" cutting depth the router shank will rub on your work and possibly burn it.
As far as crashing into your BitSetter I have no answer. I have a 4" OAL Melin bit that cuts 1.5" deep and works perfectly with my SO3 BitSetter. Just make sure your BitZero magnet is secured and not touching anything that would ground it. The BitSetter and BitZero are interconnected. When the BitZero magnet is grounded you usually get a failed probe and a probe error message.
Can you send a picture of your setup with the Z-axis positioned over the BitSetter?
In it’s highest position, the tool needs to clear the BitSetter with about half an inch to spare. If you have the spindle hanging down really low in the mount, and a really long tool, that could cause issues like what you’re describing.