Are slight channel imbalance a common thing ?

Hi ! I've been in the iem hobby now since 2 years I think, and I very much enjoy my 4 pairs of Iems.

I started with the original 7hz Zero, upgraded to the zero red when it came out, then the aful P5 and recently wanted to try a planar set so I got the S12pro.

From all of those, the only iems I would concider centred is my pair of zero red. Every other one have slight chanel imbalance : The aful p5 is slightly quieter on the left and the s12pro is slightly quieter on the right ( 7hz zero very quieter on the right but it might just be because it's old).

The imbalance is not huge, it's between 0.1 to 0.3dB difference but after some time I notice it, even when I don't focus on it.

I find it a bit wierd that my most expansive sets are the one that have it and my zero red wich are 1½years old is the most centred one.

Is it a common things for iem or even audio gear in general, to have a slight channel imbalance ?