The only reason I’ve stumbled upon this issue is that, frame by frame my target is moving to the left of the frame. Start of the seq, the target is at centre and getting to the end of the seq, the target is at the far left, So I think Siril is having issues with the stacking.
( I think my tracker ran out of battery) Hense why I want to choose reference image as one of the first images. Because Currently Siril is failing.