I’ve only tried it once in automatic and it did not actuate. The heifer went through it. I had it set on the middle setting. So I got to thinking, maybe there is an adjustment to make more sensitive to being actuated. That’s what lead me to the spring tension.
It sounds like it may have been open too wide. They need just enough to poke their head through. They have to have enough body behind the head for their head to go through and their shoulders to hit to make it close.
Bird Dog is right about barely setting that little bar in the circle hole. It's pretty hair trigger. Some times if one goes busting in there it will trip and close just from bouncing around.
Spray all the moving parts down with wd40 except the shiny, rectangular rod. Their catch system uses friction on that rod. It will also wear out with enough use.
I use the head gate on the SO4 squeeze. To be honest I got away from the self catch most of the time. I just get behind the cattle and shove them in the squeeze with the headgate closed. I close the tail gate with the rear lever. Then I manually catch them. When I catch the head I like to squeeze them immediately because they tend to stay calmer and not try to lay down. In fact I will start squeezing to get them to go through the head gate.
If you don't have a slide gate about a cow lengths before the head gate I would suggest it. Giving the cattle room to back away from the head gate makes it tough.