Transmission gear selector moving?

[Nodnarb76]

I have noticed recently that whenever I pull away from a stop my column shifter (automatic) sometimes moves to the left and if I don't hold it it will sometimes get in between neutral and drive.

Any ideas?

FWIW this is on my 87 Suburban with an 6.0LQ4/4L80 swap.
I'm using the Lokar shift linkage kit which works great, just trying to figure out why it's moving when I put a load on it?