Projectiles being weird

Hai! I'm working on a magic datapack, and many spells involve summoning arrows, tridents, etc that get thrown forward. The problem is, the projectiles can get thrown sideways or backwards depending on the direction you are facing (though they eventually correct themselves after flying through the air for long enough). Teleporting them to be facing the same direction as the player doesn't change anything. Is there a way to fix this, or is it just an annoying visual bug? (I'm on the latest snapshot btw)