There’s a lot of reasons to get these errors from copying code from one to another. I’m curious why this needed to happen in the first place. As for prevention in the future, again, why did this need to happen in the first place? Are you duplicating it because you want the same code to start from but want to alter things from that point? Duplicating the asset is better than just the code. Is that not possible because the new blueprint is a different class type? That’s prone to errors.
The error log is a lot to read through and unfortunately I can’t determine the issue from that info. What do the two blueprints look like, is there a lot of code?
This issue could be caused from a duplication of a function, event, timeline, possibly a variable. I couldn’t say without knowing what’s in it though (that’s me anyways).