What does "no surface intersection" mean?

In searching for the boundary between valid and NULL data points on JunoCam images, I implemented a bisection method for precision and after a few successful iterations I hit a strange error message:

ISIS program 'CAMPT' call failed, framelet: JNCR_2018197_14C00024_V02_GREEN_0002.cub
b'**ERROR** Requested position does not project in camera model; no surface intersection.\n'

I’m curious what this means, as the point seems to be on the image and should project?

Here’s a portion of sample output:

Iteration 0
New (x,y) coords 1419.8802532037, 72.693956780111
New Latitude: Quantity(value=34.772053745496, units='DEGREE')
New Longitude: Quantity(value=69.753646983441, units='DEGREE')
New Sample: 1419.8802532037
New Line: 72.693956780111

Iteration 1
New (x,y) coords 1419.8473194744001, 72.64083786187899
New Latitude: Quantity(value=34.905538136396, units='DEGREE')
New Longitude: Quantity(value=69.772788133242, units='DEGREE')
New Sample: 1419.8473194744
New Line: 72.640837861879

Iteration 2
New (x,y) coords 1419.8308526097499, 72.614278402763
New Latitude: Quantity(value=35.02991442295, units='DEGREE')
New Longitude: Quantity(value=69.790703563961, units='DEGREE')
New Sample: 1419.8308526097
New Line: 72.614278402763

Iteration 3
New (x,y) coords 1419.8226191774002, 72.600998673205
ISIS program 'CAMPT' call failed, framelet: JNCR_2018197_14C00024_V02_GREEN_0002.cub
b'**ERROR** Requested position does not project in camera model; no surface intersection.\n'

This is some amount of mis-alignment between the observed surface and the a priori computed surface in Junocam imagery. What appears to be happening is that in the a priori camera geometry, the look vector at that point does not intersect the “surface”.

That makes sense, Jesse. Thank you!