Layout - Modules visible instead of grey module positions

Hi,

Today i was working on our website and within the T3 Layout tab i saw modules instead of the grey module layout.

I have never seen it before on our other websites using T3? Did one of you see this appearing before? Any idea where it may come from? The moment i hit "save" all module positions were reset to default and messing up the whole website. I am troubleshooting the issue but i did not find it yet.

Jasper