Grid square warning

Im using 2010 and have been working on a route which seemed to have issues. I started with 10m grid but because of cliffs changed then to 5m grid, no problem. I later added some more boards which added as 10m grid (forgot to set them). I started getting a lot of freezes when moving around a couple of boards. On checking they where indeed 10m grids the others 5m. I then clicked on each board in turn to set all boards the same and found they had reverted to 10m grids (had not changed the board size in the add board). I then selected the 5m grid from the add board and re did the conversion back to 5m. Now I can move around without the jerkiness being as bad as it was. I thought that once it was 5m it could not be reverted back or has this changed?
So if you have a very jerky layout check all the boards are of the same grid size.

Always have been able to change back, what can't be undone properly is any textures that you have blended etc as they revert to un-blended and any changes you have done in the 5m grid will get flattened out.