Superclipping. Needs more research..
I was recently watching the progress with OpenLara on the 3DO and several people trying the alpha demo discovered sudden rare hickups/locks in the rendering. The original developer realized this was coming from the use of superclipping feature and that reminded me my recent discovery that feedback CEL textures with LRFORM flag will lock if superclipping on them is enabled while they cross certain edges of the screen. However, the developer of the port claims that the textures are regular 4bit palletized and not the 16bit framebuffer format. And the hick ups are rare there, if they were LRFORM then almost every frame would be locked to 1FPS. There is something wrong happening with the rendering of few CELs, as far as I know invalid CELs or other bugs can lock the rendering forever, and there is a timer value of exactly 1 second that can also be controlled from a function (but we don't need to), where if something went truly wrong and a DrawCel doesn't return at that time, the rendering terminates.
I might just need to do some tests later with 4bpp palettized textures and a bunch of them at various shapes in the screen, I don't know. It's strange that it happens in the case of OpenLara too, as in my experience it's a bug with framebuffer textures, but never experienced it with other linear types of textures personally, yet I haven't build a more complex 3d engine that could trigger this, most of my experiments are pretty basic.
Still, I did some other kinds of interesting experiments, like hacking my old feedback cube to move around and demonstrate the bug. Or zooming two pictures, neither of them points to the framebuffer, but one of them is stored in the zig-zag format of the framebuffer (but I assume it's loaded in regular ram, although I haven't checked of LoadCel does something weird) yet still triggers the bug. I used a tool called BMPto3DOCEL which the author made it read a BMP and extract a CEL file, but there are not enough options and it always saves a 16bit CEL in framebuffer format. I did hack that tool to produce a linear format, as I thought the framebuffer format shouldn't be used (or at least doesn't make sense) for regular textures, only when you point to a backbuffer in vram to do feedback effects. But there is something interesting I also noticed about performance.