This issue is reproduced on iOS 15.6 for some Verge3D applications. E.g: The app which crashes https://cdn.soft8soft.com/demo/blender/metaballs/metaballs.html The app which does work https://cdn.soft8soft.com/demo/blender/spinner/spinner.html When taking screenshots using Side button + Volume up (iPhone 13+) or Side button + Home button (earlier iPhones) the browser freezes completely. The bug appears to be not connected with Verge3D specifically.
Looking at the stacks, seems kinda similar to bug 237674, insofar as the UI process is blocked on -[_WKWebViewPrintFormatter drawInRect:forPageAtIndex:] + 116 (_WKWebViewPrintFormatter.mm:95).
<rdar://problem/98885447>
Far as I can tell, this doesn't reproduce on iOS 16 Beta, so I'm assuming this was fixed elsewhere.