This is a solid body but turned into strange boy after fillet has been applied to edges. What is the reason for that?
I'm not in front of my pc. But according to your video, if you right click Loft5 and select Change Transparency it'll be back.
Either you have a surface (or 2) set to transparent or you are having a graphics card driver issue.
Maybe it's having hard time merging
Loft surface then turn into solid gives correct result. I do not know why.
Knitting takes care of the small gaps.
Okay now I can remember a YT video. It is said that group of surfaces formed a solid. Surface extrude gives you only one surface at a time whereas solid extrude gives you many surfaces at a time.
I'm not in front of my pc. But according to your video, if you right click Loft5 and select Change Transparency it'll be back.