as title states. the vehicle plasma cannon sometimes fires in the exact opposite direction of the enemy.
IE: all enemies ahead, and it instead fires behind, about the same distance.

this seems to be influenced by my own movement.
this has been tested with both the MK1 and MK2, further tiers are not available to me

I'm guessing that it's because of the plasma turrets' minimum range. It's predicting where the biters would be if they (and you) kept going at the same rate and same direction.

I'll check if aiming prediction is enabled and see how it feels if I turn it off.

ahhhh... that would make sense.
so. if I stay far enough back this shouldn't happen, right?

I just wish it would priority target the nests/worms in the distance, since the biters can be dealt with with lasers

I think it does use predictive targeting, because it has that "Artillery range" type of firing distance, and before I edited it to add predictive targeting, it would usually just aim where the enemies were, and kill nothing.

So, maybe there's an error in predictive targeting that doesn't account for attacker's movement very well.

the issue still persists.
is this an issue with your mod, or should I report it to the factorio devs.
(P.S.: I can provide screenshots)

edit: setting target lead to 0 works as a fix. dunno why, but it does.