Blue grip arrows (instance parameters) won't snap to objects

[patricks]

I have a family for a base cabinet filler piece that has the width as an instance parameter. Since the "width" parameter cannot be changed in the default casework template, I can only assume that this family was either started as a generic model and then changed to be a casework family; or it was started using the casework template, changed to generic, width changed to instance, and then changed back to a casework family.

All of that to say, the blue grips that show in plan and elevation due to the width being an instance parameter will snap to the sides of other cabinets, walls, etc. I can also align each side of the filler piece to a wall and to the side of another cabinet.

Now the issue is with my wall-hosted wall cabinet filler piece. It's a casework family, so I changed it to generic, changed the width parameter to instance, and changed it back to casework.

When I place this filler into a project, hosted by a wall, the blue grip arrows for width will NOT snap to walls and other cabinets. If I try to align the sides of the filler, it moves the whole object instead of actually changing its width.

Why will my base cabinet filler change its length (stretch) when I align an end to another object, but the wall cabinet filler maintains the same length (moves) when I align one end?