When have a shot SpectralArrow (or any other arrow) and try
/effect @e[type=SpectralArrow] glowing it's not affected.
Even if you try
/effect @e glowing it is unaffected.
This might be working as intended though.
MC-84233
Arrows cannnot be effected glowing
Resolved
Works As Intended
0
effects can only be given to mobs and players, not all entitys, an arrow is an entity, but not a mob, so this works as intended