Trouble understanding answer to quiz.

Question

I reported this as an issue, and perhaps should have brought it up here instead. For one of the quizzes, the answer is

A veces __me olvido de__ que llevamos casados 20 años. (Sometimes I forget that we've been married for 20 years.)

I noticed that the verb *olvidar* is being used intransitively and that, even though the "accidental se" is being used, that olvido is not in the third person. (It's not in the preterite / no accent on the o). I'm having trouble finding an example of this on the lesson page.

Thanks!

Answer

It’s the same form as the second example in the lesson:

Me he olvidado de [ las llaves ]

A veces me olvido de [ que llevamos casados 20 años ]

I used square brackets to show the phrases that are functioning as direct objects. Also note that we are using the present reflexive form in order to represent a repeated action in the present.

Cheers!

Answer

Hola Tony 
As Marcos said, the form that we chose as correct is "A veces me olvido de que....", using the verb as usual, i.e. agreeing with the person who forgets (yo / olvido) but it's also using the verb as reflexive and add preposition "de" - this is the second structure explained in the lesson. You can see the example Marcos took out of the lesson : Me he olvidado de las llaves
The accidental se is the one that works differently in terms of agreement. See how you can say the same thing with the accidental se:
Se me han olvidado las llaves.
Here the subject is the thing that you forget (las llaves) and the verb is now matching with the plural "they": "han olvidado". 
I answered this question from the Help Desk too, so you may find a more extended explanation there as well.
I hope it helps
Saludos