I do have purple question mark as well but only on the mid air homing projectile, if I shoot without lockon there is no question mark.
I was playing as client on automaton mega factory, host probably didn't have the mod
for mod loader, I put bingus share loader(number 254) at the very bottom of mod list and homing stim(number 251) above it.
priority is default I think "set last mod to hightest priority"
with that purple mark shenanigans aside, the mod work beautifully, I can finally role play as medic easily
"Unexpected error while loading game files. Check for any data that may have been modified or corrupted from the initial install. (Error code: 0x42554E444C45)" Why? I didn't get this error when I installed another mod (P-11 Self-Hit Healing). The error appeared just as I saw the Super Destroyer, and then the game froze and crashed.
with the lastest Im no longer see the purple question mark.
for the question at that time, I do see it and other player (random so probably don't have the mod too but idk) also see it as purple question mark homing to them.
have not ask other after the updated but so far nobody say it so I guess they also dont see purple question mark