Photoshop has many limit all applications have them. One I think you may be running into is Photoshop Canvas size. The Canvas maximum width and heights are 30,000 pixels. My Canon 1D Mk IV is a 16 MP camera in portrait mode its image size is 3264 px x 4896 px. You should have around 40% overlap when stitching images. 60% of 3264 is a width of 1958. I was a junior in high school in 1958 the fifty music was in full swing. Anyway I do not think I could do 17 images for 17 times 1958 = 33,293 Pixels. The Canvas width would exceed Photoshop canvas size limit. You would need a Application specialized for stitching huge panoramas.