From
http://www2.usfirst.org/2005comp/Sec...-The_Arena.pdf
The scoring objects are made of PVC and are expected to undergo extensive robot and person handling. They are likely to become misshapen and some edges may become slightly bent instead of straight. Because of a variety of environmental conditions at various competition sites, their resilience and durability are expected to vary. Slightly misshapen scoring objects are expected, and they are considered to be part of the game challenge.
I couldn't find where I read or heard this, but from what I know:
The field attendants will try to place them the same way each time but there may be slight variances in their positions.