Dinnyés Dániel writes:

> I have tried reproducing it with a minimal example, and this seems to work
> for me:
>
> * FOO
> ** TODO baz1
> SCHEDULED: <2020-08-16 Sun>
>
> some text
>
> * BAR
> ** TODO baz2
> SCHEDULED: <2020-08-16 Sun>
> *** DONE baz3
> SCHEDULED: <2020-08-16 Sun>
> *** TODO baz4
> SCHEDULED: <2020-08-16 Sun>
>
> When in the agenda, on the front line of item baz, setting it to DONE state
> works fine.
> OTOH, when going to the end of the line on the item baz, trying to set it
> to DONE results in the error message:
> TODO state change from TODO to DONE blocked (by "TODO baz4")
>
> Also, I have (org-enforce-todo-dependencies t), which causes the blocking,
> and (org-agenda-dim-blocked-tasks (quote invisible)), which hides baz2 from
> the agenda... because of this baz1 is followed directly by baz4 in my
> agenda window.

Thanks for the minimal example and configuration.  I can trigger the
issue using that file and

    (setq org-enforce-todo-dependencies t)
    (setq org-agenda-dim-blocked-tasks 'invisible)

with commit 5e4542d69 checked out.

The issue doesn't happen with the current release (v9.3.7) or the master
branch.  It went away with 27e4d7ce4 (Prevent infinite loop when showing
new time in agenda, 2020-02-14).  I haven't taken a closer look, though.