Does anyone recall an old show with warring robot factions where it turned out that if they had human pilots their (previously dormant) weapons systems worked? I think this became apparent after some humans crashed onto their planet and the humans discovered cockpits inside the robots.
I know this sounds like the Transformers S4 rebirth arc, but I was pretty sure that the discovery was accidental unlike the deliberate bonding that happened in that show.
I watched it on VHS with English audio in the early 1990s. Can't remember whether it was a movie or series with an ongoing plot.