For some reason selecting new blueprint contents for a blueprint that has an absolute grid will destroy your offsets. Especially when rails are involved.
I considered raising a bug report but it doesn't feel like a new bug in Space Age, so probably not a priority.
As an example/demo:
Good offsets If you then simply click the blue plus to select new blueprint contents and select the exact same objects, you end up with this:
Bad offsets (I want the big power pole in the middle, not off by 1)
To fix this and recreate the original offsets I must:
- unselect `Snap to Grid`
- select new contents for the blueprint
- reselect snap to grid
- enter the offsets again manually