Fit complaints usually describe a symptom. Fixing them requires identifying the pattern cause, which is often located somewhere other than where the problem is felt.
Pulling across the back or chest
Usually insufficient width or incorrect armhole shape. Adding overall width often makes the garment large without solving the pull, because the constraint is the armhole rather than the circumference.
Gaping at the neckline
Often a neckline cut too wide or too deep for the shape, or a facing that has stretched during construction. Stabilising the neckline usually helps more than reducing the opening.
Twisting side seams
Frequently a fabric issue rather than a pattern issue, caused by yarn torque in knits. It appears after washing and cannot be patterned out, so it must be caught in fabric testing.
Riding up
Commonly caused by insufficient length or a body that is too narrow, so the garment climbs to a wider point. Length alone often fails to fix it.
Sleeves that restrict
Usually armhole depth and shape rather than sleeve width. Widening the sleeve without correcting the armhole rarely resolves restriction in movement.
Diagnose before adjusting
Change one variable at a time and re evaluate. Multiple simultaneous adjustments make it impossible to know which change worked, and often introduce a new problem elsewhere.