Steps to reproduce:
1. Make a blueprint from something that's built on the map and enable "Snap to grid". Make sure it's set to Relative. Setting custom size or position is optional. The automatic grid position will be as expected, at X=0 and Y=0.
2. Save the blueprint.
3. Go into the blueprint again and select new contents (selecting exactly the same contents still produces this bug).
Result: the grid position will be nonsense unless it happens to be the same as it was previously. If the same entities in the world are selected as the new contents several times, the resulting nonsense grid position will also stay the same - my guess is that the game remembers the original coordinates of the entities relative to the world, and sets the grid position to (0, 0) relative to the world, which can be many blocks away from the actual entities.
Expected result: the grid position will be automatically set the same way as when making a new blueprint (at 0, 0 relative to the blueprint), or, alternatively, it should be kept the same as before selecting new contents.
[1.1.1] Selecting new contents for a blueprint with a relative grid sets nonsense grid position
Re: [1.1.1] Selecting new contents for a blueprint with a relative grid sets nonsense grid position
Although the underlying problem might be the same, the actual issue is still different, as this happens with blueprints freshly made in 1.1 and from the same entities as those already in the blueprint.