Trouser problem- weird curved leg/crease

What on earth would cause the problem in the attached pic? I don’t experience this with other trousers. They are being worn as straight as I can get them. (And my legs are not bent or anything .)

Just bad construction?

My wife, who makes most of my trousers, speculates on two suggested problems. Firstly it could be that the panel, that's the section that will become the trouser leg, moved when being cut out. By move she means that mass produced garments are cut out in bulk, perhaps a hundred at a time. If the press holding the fabric wasn't locked tight then the panels could well come out mis-shapen. This is what a trouser panel means:

The other reason could be that the trouser legs were not sewn together correctly. She adds that if it's either, or, then send them back. The amount of unpicking, correcting and re-sewing would be more expensive than replacing them. On the other hand, if they are just a cheap pair, maybe it's just not worth all the hassle.

They are military uniform pants most likely from the late 40s/early 50s

I would say so. However, the comment above posted really great points.