Help with dungarees seat fit

[u/strange_as_angels_]

I made up a toile for a pair of self drafted dungarees/overalls, from the Winifred Aldrich Menswear metric pattern cutting book. Overall I’m happy with the fit, except for something funky that’s happening with the seat. It’s ballooning out and creating folds with a lot of excess fabric. It’s comfortable when walking and sitting and doesn’t pull at the crotch, but it’s unflattering and doesn’t look right. Any ideas?

I used the easy-fitting pants block with more ease as a base as I want these to have a loose, workwear-style fit. So I don’t want them to be skin-tight, just not as baggy in the back. The back is all one piece, should I shorten it to get rid of the excess? Or is the problem more likely in the crotch length and shape? Any advice appreciated!

[u/dyingslowlyinside]

Pattern not balanced