When you pick a sizeable with the Default Cursor tool, it moves to the block the cursor is pointing:

However, with A.I Rect Cursor it's a bit different. When the cursor reaches the half of a block, the object moves into the next block:

To explain it better look at these images:
- Spoiler
- Default Cursor grid:

A.I Rect Cursor grid:
So for a weird reason, the A.I Rect Cursor (and probably Rect Cursor) is not calibrated correctly, it auto-aligns blocks with a different offset than Default Cursor does.
Now the reason why I'm reporting this is because it affects a lot in how you put sizeables. This inconsistency of auto-align cause this:
- Spoiler

So please make A.I Rect Cursor match Default Cursor auto-aligning.

