Last night I read my test chart containing 6 pages, saved each finished measurement and imported it in PM5's compare tool. I made 6 measurements, and comparing these, all had about average 0.8-1.4 I deltaE2000. I tried moving the paper on the table each round to see if there were something to do. As you said, the head angle isn't flat against the paper, and as it swivels the angle changes. Tried adding 6 papers underneath my chart to raise it, holding it stuck with tape, and it Acutally worked better.
Strange to think the angle from the head against the paper is wrong from the manufacturer?