"a linguistic slip"

[Odessa Dawn]

"What I said about Safed is my personal stance. It means nothing about giving up the right of return," he said, claiming the Israeli news network had deliberately edited his statement to misrepresent him.
Palestinian officials claimed the phrasing was a linguistic slip by the president who was interviewed in English rather than Arabic.
More: Mahmoud Abbas denies that he has given up on Palestinian right of return - Telegraph

Does linguistic slip mean slip of the tongue, mistranslation, or error?

 

[HanibalII]

"What I said about Safed is my personal stance. It means nothing about giving up the right of return," he said, claiming the Israeli news network had deliberately edited his statement to misrepresent him.
Palestinian officials claimed the phrasing was a linguistic slip by the president who was interviewed in English rather than Arabic.
More: Mahmoud Abbas denies that he has given up on Palestinian right of return - Telegraph

Does linguistic slip mean slip of the tongue, mistranslation, or error?

I'd say closer to mis-communication. Experiencing linguistic barriers, which makes comprehension more difficult.