I used to hate hsts but I’m stubborn and was determined to figure them out. Don’t give up.
When you’re stitching your hsts together it’s important to make sure you have a consistent 1/4 inch seam. Sometimes we can go off a bit when we’re coming to the end of the seam. Feed dogs can also make us not keep the 1/4 inch all the way to the end. Use a stylus to keep the fabric up against your presser foot as you are finishing your seam.
the advice from snooze 2978 addresses your problem, too.