My guess would be your tension level, that is to say...you're nervous, and you're holding those circs with a tense grip.
But in the end...knit with whatever type of needle best suits you.
If you must knit something in-the-round using circs...try other methods of knitting with circs in-the-round. I personally use the two-circs method of knitting in-the-round on small diameter things. I'm much less tense. I switch to a single 24" circ as soon as possible.
I use one 24" Harmony circ and one 24" Nickel-plated for my two circs. The NP hold the first half of the stitches, the Harmony holds the last half of the stitches. No confusion where the round begins and ends.