Updating this thread with a response from @Figma_Support about this issue.
I’m not able to test for repro there as it uses a custom font, but this might give us a clue to what’s causing this.
The main reason we see font styles detach is that there are conflicting fonts used by editors on the team. Our back end dashboard for this problem is showing conflicts for your font Circular Std which looks to be used on the elements you’re pasting from.
We suggest that you have all editors remove these fonts if they are locally installed. Then please ask all editors to install the same version locally. After doing so you will need to restart Figma to serve the correct font version.
If this is affecting component appearance you can launch quick commands (cmd /) then use the “Regenerate all instances” tool to refresh all of your instances at the same time.
If it is affecting text or style appearance or settings outside of components you can use quick commands to “Select all with same font” and then “Recompute text layout in selection.”
Let us know if you have any questions or continue to have trouble after updating those fonts and we’ll be happy to help!
I do not believe this bug has anything to do with the custom font. I have since responded to support with an example that uses the system font Arial. The issue persists. I will report back with @Figma_Support’s answer as soon as I receive one.