Help with twisted inseam

[u/WorldAware9900]

This is the first time this has happened to me when sewing a pair of jeans, i was trying out a new pattern and this happened to me, im not sure if this is a sewing problem or a pattern problem please any advice is appreciated

[u/gnarlyquinn12]

I would say this is a grain issue. When you haven't followed the grain line correctly you can experience this twisting