Drift with 1d Mark4+Markins Q3 + Gitzo combination

Hello,

I am using the following setup:

Markins Q3
Markins PG50 Plate
Gitzo GT2531 Tripod legs
Canon 1D Mark 4 (41.6oz)
Canon 70-300 f4-5.6 lens (22.2 oz)

Here is my problem:

with lens at 300mm, I first autofocus on a subject.Then, if I look through the viewfinder, I can clearly see some drift. And resulting the images are not sharp.

Has anyone experienced anything similar? The setup was working fine with my 5D (Classic) with its own baseplate.

I am way below rated weights for both the ballhead and the tripod legs.

Thanks for any information.
Ihtisham