Last month I learned something new! ;-)
I had this problem with stitching horizon lines over sea.
Can't really recall that happen before, the usual "cannot stitch", missing pictures in a Sphere-/Pano have been the pictures direct under the bird, at least if over water.
So some valuable forum members pointed me in the direction of a (discontinued!) proggy, Autopano from Kolor.

And it is doing the "trick"

Don't get me wrong, I love the easyness of ICE, select the pictures, let ICE do the rest.
Decide what tom highlight and how you wanna export it, for me (on PC) that is still the best (easiest) option.

But: ICE is not giving any option for "helping" the prog to  sort the pictures (not that I aware of, at least)

Here now comes Autopano in play.
I am still learning, trying to understand what I have to look for in the prog, but I'd like to show you one of my Sphere Pictures from Dishui Lake, Shanghai.

First how I could stitch it together with DJI and second how it came out with Autopano PLUS positioning the center pictures myself.

1. ICE
2.Autopano

And wasn't it all about the sculpture in the middle of the lake?

Wow cool picture...this lake looks on maps like made for a sphere  :-)

https://goo.gl/maps/dsz3ytYDatTaP9iZ9

MartyTravels Posted at 12-18 06:48
Wow cool picture...this lake looks on maps like made for a sphere  :-)

https://goo.gl/maps/dsz3ytYDatTaP9iZ9

Man-made 2.5km lake, perhaps DJI had Spheres in mind and something to say about it?

Hi Thank you for sharing this nice image you have captured and your insights. Nicely done and thank you for your valued support.

DJI Paladin Posted at 12-18 08:24
Hi Thank you for sharing this nice image you have captured and your insights. Nicely done and thank you for your valued support.

Thanks a lot!

Nice capture!

Arnie R Posted at 12-18 15:12
Nice capture!

Thank you!

Nice capture

Cool!

DJI Panda Posted at 12-19 00:31
Cool!

Thank you, Panda!

S-e-ven Posted at 12-18 08:27
Thanks a lot!

You are more than welcome and thank you for your valued support.