I think all of the graphics are chroma-keyed and they can remove parts easily. They can usually add or remove graphics whenever they want.
You don't chroma-key graphics. Chromakey is replacing a colour in the video signal with another image.
They of course will be able to show only certain elements of the graphics as part of normal operation. When they first came back on Pricedrop they were faulty - the bit missing was a strip across the side
I noticed on screen that they could hide part of the graphics (such as the price), if you've ever used the Mac application CamTwist you'll know what I mean.
That's what I thought. I am still unsure whether I believe the 'missing' parts of the graphics.
Without knowing their set up, it's more than possible that the final set of graphics you normally see come from more than one source, and while they've managed to get one up and working another is giving them problems.