Internal wall does not print in horizontal print orientation
I think this is caused by the shape of the hole. The shape is parabolic or circular, this means that if you slice it as in the green part, the slicer determines the placing of the layers along the curvature. If it has a shallow curvature, and slicing layer height is relatively thick, the curvature of the object cannot be followed. But, if you have more than 1 top layer, this usually should not be visible. I don't think that you have a single layer, so this is a pretty odd anomaly that I have not seen yet (that you look at the infill without top layers).

You could get past this by using a local different infill, e.g. 100&nbsp;% infill. You can look at this answer of the question: "Different infill in the same part". This should help you out printing in your preferred orientation.