I have the same problem. You don't need to go into the material room, at least not if your posing window is undocked. Just tug on the side of the window like you're going to expand it, and the inner scene will pop back into place.

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Hardware: AMD Ryzen 9 3900X/MSI MAG570 Tomahawk X570/Zotac Geforce GTX 1650 Super 4GB/32GB OLOy RAM

Software: Windows 10 Professional/Poser Pro 11/Photoshop/Postworkshop 3