In Portfolio, when a user:

Creates an Epic X inside an Initiative Y

, then

Adds them to Agile via the "Create and link new issues" command (in the Initiative dropdown)

Portfolio instructs Agile to create is a 'X blocks Y' link.

Now, in Portfolio, after some planning session where X is deemed more appropriate under a different Initiative Z, the user:

Moves Epic X to Initiative Z

Now, Portfolio does not instruct Agile to set any links.
Ideally, it trashes the 'X blocks Y' link and add an 'X blocks Z' link OR updates 'X blocks Y' to 'X blocks Z'.

Otherwise, we have a false positive:

X blocks Y is wrong

AND a false negative:

X should block Z, but it doesn't

This dependency is extremely important for all teammates that live in Agile and not Portfolio. It also adversely affects Agile-based plugins that leverage links (there are many).

Manual management of this is excessively time-consuming after each long-term planning round, because long-term planning is (meant to be) done in Portfolio.