https://www.missouriquiltco.com/shop...-missouri-star
When I have problems such as you are describing, it is usually due to my not squaring up my HST's properly. This seems to be a good site to describe how to do it.
https://www.diaryofaquilter.com/2013...triangles.html I used Mr. Google and searched for How to Square up Half Square Blocks. There are so many good websites out there.