Virtuoso Layout: instance boundry

Hello everybody,

I sometimes see a strange behaviour when creating a layout in IC6.15:

Starting at some time (do not know when/why) doing a fit does fit the layout in the middle of the layout editor, but there is a huge black area around it. So the size of the layout (rectangle form) shown is <<50% of the available area in x and y direction. When adding this block into an other layout, Virtuoso indicates a very big device size/boundry (dashed line) when hoving over the block.

I know this might happen if a small device/path/contact is placed outside of the main layout block (and due to its small size it might be nearly unvisible).

But: I (and my colleagues) have checked for such things about 100 times (including changing the visability and selectivty of layers, changing the shown layers at the Techfile, marking & deleting everything outside the block, ...). We are absolutely sure that there is no device left outside of the instance's boundry!

Has anybody an idea what might cause this behaviour and how we can get rid of that effect?

The only way we found yet, is to copy the whole layout into a new layout cell...

Thank you very much!

Best regards,

Markus