Xbox director of program management Jason Ronald confirmed in a Twitter response to a fan that Microsoft is aware of some issues with the console's current sharing experience. He wasn't able to give specifics on what's being fixed or changed, but he did confirm that it's "a priority" for the team.
We have heard the feedback and working on a number of improvements to the capture and share experience. Nothing to share yet, but a priority for the team.January 26, 2021
The addition of the Xbox Series X share button makes it clear that Microsoft is putting more value in screenshotting, clipping, and sharing games this console generation. The button can be used to instantly record video capture with automatic upload for recent clips, but ever since launch players have noted that the sharing experience sometimes seems to strain the console. This can result in unexpected delays, glitches, and even difficulties in sharing the content in question - which can make that cool new button feel less useful than it should.
Fortunately, Microsoft has set a solid track record of responding to Xbox Series X issues spotted by the community so far. Its latest title update fixed 4K Blu-ray black levels after an enthusiast YouTuber noticed they were slightly - but very annoyingly - too bright. Fixing up the sharing experience may take some more work than that, but at least we know Microsoft is on the case.
Ronald also confirmed that Microsoft is still working on Xbox Series X backwards compatibility improvements, and it will have more news to share this year.