Abdu'l-Baha mistakenly calls Ja'far al-Sadiq "the seventh imam"

In a letter to Adib, Abdu'l-Baha calls Ja'far al-Sadiq "the seventh imam." Of course, Abdu'l-Baha likely knew Ja'far was the sixth imam, so it's a very minor mistake. He's a normal human, so you'd be right to shrug and say "who gives a shit." But for Baha'is who adopt the maximalist position that Abdu'l-Baha never made a mistake, it's a problem.

The letter is found in Mazandarani's Asrar, 1:82-3 (Phelps AB03482), which I typed up below. The context is the Constitutional Revolution, which Abdu'l-Baha says he asked the Baha'is to stay away from (there's a paper on the subject here). Sayyid Ali Akbar, who he mentions in the letter, kept him informed from Iran. Abdu'l-Baha is frustrated that some of the Baha'is aren't heeding his directives so he throws up his hands and says that God had other plans (a Shii idea called bada).

هو اللهان منادی پیمان ... در بدایت انقلاب ( انقلاب مشروطیت در ایران ( عبدالبهاء بنهایت همت کوشید که یاران بی طرف مانند و خیر دو جهت باشند ملاحظه شد که بعضی تأویل مینمایند و مداخله میفرمایند و نتیجه آنست که حکومت بهانه نماید و ماده بعضو ضعیف ریزد و جميع احبای الهی را قتل عام کنند و واسطه صلح نمایند و بسبب این قضیه حکومت نفوذ شدید یابد و اقتدار جدید نماید جناب آقا سید علی اکبر را احضار نمودم گفتم که آنچه خواستیم یاران را از مداخله منع نمائیم ممکن نشد بعضی مایل به مداخله هستند و این نتایج مضره بخشد حال محض اینکه این مداخله را منع نمایم میخواهم که عبارتی در حق مرکز سلف نویسم اگـر چنانچه باید و شاید قیام نماید فبها والا از قضایای مسلمه امر الله است . به حضرت امام جعفر صادق گفتند که ما منتظر معصوم سابع بودیم و سابعهم قائمهم میگفتند چگونه شد که تحقق نیافت فرمودند آن سابع منم ولی بدا شد خلاصه بمومی الیه گفتم که در قائمیت اما جعفر صادق بدا جائز بود حال اگر چنانچه باید و شاید معمول نگردد بدا سهل است .

He is God!

O herald of the covenant….At the beginning of the (Constitutional) Revolution, Abdul-Baha tried very hard to ensure that the friends remained neutral and well-wishers of both sides. It was observed that some were misinterpreting (my instructions) and interfering. The result is that the government uses this (interference) as a pretext to weaken and eliminate a member (of parliament), massacre all the divine loved ones, and make peace through mediation [i.e. play the peacekeeper], thereby allowing the government to gain significant influence and assert new authority.

I summoned Aqa Sayyid Ali Akbar and said, “We wanted to prevent the friends from intervening but it was not possible. Some are inclined to interfere and this will have harmful consequences.

Now, simply to prevent this intervention, I want to write a statement about the center of the predecessors [the Qa’im]. If he arises as he must and should, then good; otherwise, it is one of the settled decrees of God. They said to Imam Ja'far Sadiq, “We were waiting for the seventh infallible (imam), for as the (imams) used to say 'the seventh is their Qa'im.’” When asked why it did not materialize, Ja’far said, “That seventh is me, but bada happened.” In summary, I told (Sayyid Ali Akbar) that for Ja’far Sadiq, being the Qa'im was permissible. If something does not happen as it should, it is simply bada.

https://www.reddit.com/r/exbahai/comments/1co10og/abdulbaha_mistakenly_calls_jafar_alsadiq_the/