Line trace to surface x,y

Hi there. I wish to perform a linetrace and get an x,y of the surface it hits, I can work out how big the grey surface is by the scale, which in in millimetres (A plane exported at 1mm square) and I can figure out the hitr location. I’m just struggling to get it 100% working. Right now it falls apart if the big grey surface is rotated in any direction other than straight up, y facing. I do not know why this is.

Please see pictures.
Pic 1, here it is in and working just how I want, the issue is if i rotate the big grey surface it breaks and no longer works. This is something to do with the way unreal represents rotations and how I’m getting that information in the blueprint, however I don’t know how to fix this issue, or even where the issue is happening!

Pic 2 is my desired end-goal

Pic 3 is the current blueprint which only works when the grey surface is facing in the y direction.

Pic 4 is the garbage my blueprint returns when i rotate the big grey surface 90 degrees, Can anyone offer any insight?

Many thanks for looking! - Luke.