In Drona Parva/Jayadhrata vadha parva, Sanjaya says:
I myself, with my own troops, cased in mail and equipped with weapons, and supported by four hundred foremost of bowmen, resisted Chekitana.
Ganguly's footnote for this also says:
This Sloka occurs in all the texts. It would seem, therefore, that Sanjaya was not always a witness only of the battle for narrating what he saw to Dhritarashtra, but sometimes at least he took part in the battle.
Are there any other references where Sanjaya did actively take part in the war and was not only a spectator?