SC2Mapster

Then I am out of ideas as to why that is happening.

What is the Validator: Range field set to for your validator?

More likely it uses the Movement: Inner Radius field.

Probably would need a Create Persistent effect that validates the offsets from the caster to the target point. That could ignore all offsets behind the caster and then validate until it hits an obstacle in which case it uses a fallthrough effect.

With units the Movement: Radius field determines the collision. Still by being units they could be detected by an enumerate area validator.

Problem is enumerate area requires units to count so unless you want to check if it is a unit/cliff and then see if placement fails for it to be a doodad. That would require a Function type validator to process.

Putting it in the effect after would get it to validate the point at an offset from the missile which for fast moving ones could give enough time to make a course correction.

Try putting your validator in the effect after the create persistent. That way you might be able to calibrate for infront of your missile to adjust for insane speeds.

That is correct that it will look for a valid placement within so much distance from the point.

2. Yes the Effect: Periodic Offsets can be set to be relative to the facing of the unit using the Target: Location Value field.

I would validate the source point and use a Create Persistent effect with an offset just behind the unit.

Unless you give the missile unit a placement footprint and use a Placement Location validator I cannot see a solution.