Spawning a particle to move along a path between two points

I've been trying to make a particle spawn with the correct direction (vx,vy,vz) to move from one point to another, and have been struggling with it for a while now.

So, I'm wondering if anyone in the community may be able to shed one light on why my current work isn't exactly working!

Particle properties:

particle properties

Spawning block:

spawning block

in case it may be hard to read, the spawning block is as follows (split into multiple lines for readability):

Spawn single particle at x: [x] y: [y] z: [z] with

vx: 0.5*((get NBT tag "target_x" of block [x] [y] [z]) - [x])

vy: 0.5*((get NBT tag "target_y" of block [x] [y] [z]) - [y])

vz: 0.5*((get NBT tag "target_z" of block [x] [y] [z]) - [z])

type: CUSTOM: ParticleDendro

The "target_x/y/z" NBT tags are the corrosponding coordinates of the target block ie, where the particle is going. These are being set and are usable via other processes I have using these NBT tags, so I am sure that the tags are not an issue here, unless it has something to do with server/client desync which I hope is not the issue.

thanks in advance for any insight into this issue