Board gets wider at the end of a cut with the CSM

I've been cutting some boards with a logosol big mill chain saw mill. Saw is a Stihl 660 with a Logosol narrow kerf ripping chain. The big mill has a rail that you fix to the log and slide the saw along in a jig. I'm finding that the thickness of the boards is about equal at the sides of the start of the cut but not at the other end. At the end of the board the closest edge is again in good agreement with the thickness at the two sides of the start of the cut but the width on the other side of the cut at the end is generally wider ie the saw is cutting deeper into the log on the far side at the end of the cut.



Looks like operator error on my part but I'm not sure what I'm doing to cause the increase in width on the far side at the end of the board.



Grateful for any advice on what I'm doing wrong and how I might fix it



MAI