Learn English – An adjective to replace “so random” (to describe one who is apt to say random things)

Among friends, we describe a person as "so random" (he/she is so random) if that person says random things (often in group discussions). That is, we do not use it as defined below (i.e., he/she is "so odd").

random (informal, LDOCE #3):

strange, unusual, or unexpected

She's great – she's just so random!

odd (ODO #1):

Different to what is usual or expected; strange.

Therefore, I suppose we're misusing the informal random because the people we're trying to describe are not odd in general (or wonderfully odd like the Luna Lovegood character). They just come up with "the weirdest stuff" sometimes or come "out of left field" a lot (so to speak).

Question:

Is there an adjective to describe one who is apt to say random things (i.e., not a word that just means odd basically)?

If not, an accurate phrase (short and contemporary if possible) would be helpful. Thank you.

Update (20 May 19)

I stumbled upon this definition in Wiktionary (via a link found in a language log).

random (adjective, #6):

(colloquial) Characterized by or often saying random things;
habitually using non sequiturs.

You're so random!

So, other people use it as we do, but it seems to be uncommon (and dated); that makes sense.

Thanks for off-the-wall (and offbeat); I forgot about them.