Try using healing bush tool, or clone stamp. Set the hardness of the brush to about 50 %, except when your close to a significant color/tone change, to avoid edge blur, change the brush hardness close to 100%.
Photoshop Sky replacement may not create a perfect mask every time things like mast or a beam may through Adobe AI a curve ball. Don't worry too much over that. You will be ably to work on Adobe mask after you commit to a sky replacement to add the missed area to Adobe mask. Here is an example a beam through Adobe's Ai off.
The issue in my case is that the AI didn't replace and mask all the way across the pic. The mast seemed to force a stop completely. Similar to your example but your sky was still replaced all the way down.
Interesting but, I'm sure it'll get better as time goes by and more pics and scenarios are handled.