It looks like underburn but you say it’s not? I’ve had these burn nice blue on diesel. For all these issues is why I went back and stuck to the Optimus 199 and 111t! No issues and they already have the silent cap from the factory!
I think from what I see your stove needs either a smaller jet or more air!
I think in my opinion the silent burner is the issue in not letting the fuel burn properly, I would revert back to the flame spreader, as the yellow flame is not good when cooking.