I have experienced exactly the same with WinUAE, all different versions I've tried. Randomly (not all that often, though) it just shuts down and throws me back into Windows. It has got nothing to do with P96 in my case, since it has behaved this way both with and without P96 running.
Other interesting bugs I've encountered are the following:
Bug No. 1: If I run Workbench with the P96 drivers every now and then the pointer leaves trails and trashes the grahipcs on the screen. This bug has followed me since the very first time I tried WinUAE a couple of years ago and has also been true for all of the different systems I've tried WinUAE on.
Bug No. 2: If I run Workbench without the P96 drivers and without the filtering option turned on, the pointer radiates garbage on the left and right sides of the pointer, making the screen unusable as soon as I've played around a bit with the pointer. This bug appears not always, but in like 90% of the time.
Bug No. 3: What always happens when running under the same conditions as in Bug No. 2 is that the screen jerks around really much when I try to drag it up & down. With 'jerks around' I mean that the view jumps up & down, sometimes all the way up to the top of the screen, no matter how far as I have currently dragged the screen. As soon as I stop dragging the screen stops at the point I've dragged it to.
Bug No. 4: If I turn the filtering option on to avoid Bugs No. 2 and 3 the speed of the JIT emulation drops too much to be logical. Things like copying files takes ages compared to how long it takes without filtering turned on. So, working under WB without P96 installed, using the filtering option to be able to strech the view of Workbench, making it use 100% of the screen instead of having the ugly borders that comes when not using filtering, makes it at times even slower than my real 060 Amiga.
Bug No. 5: If this bug still is persistent I don't know since it got on my nerves to the point of me not bothering about using the very option that triggered it anymore. Anyways, when checking the bsdsocket.library option in WinUAE surfing the net didn't work. I thought. Until I realised that if I started up IBrowse, tried accessing a page, and then pressed the WinUAE configuration key (F12, is it?), it seemed to load a tiny piece of data during the time from the key was pressed until the WinUAE configuration GUI popped up. So, to be able to browse the net, transfer files over the net, or whatever the like I realised I had to press F12 and then ESC and then F12 and then ESC extremely fast and many many times to even load up a simple HTML-page. The last time I bothered to try was something like a year ago, and by that time all of my friends that I asked encountered the same bug (but they didn't know that they at least could get the data transfers to work somewhat by pressing F12/ESC, they just thought that bsdsocket.library emulation didn't work, but when I told them they tried and experienced the same thing).
All of the bugs mentioned above, besides No. 5 which I don't know if it still is there to be found, I've encountered on every system I've run WinUAE on no matter what version of WinUAE I've tried. Different processors running at different speeds with different hardware added to the motherboard.
I can't understand how come that these bugs haven't been adressed, since alhtough apparently not everyone, but many people have experienced them. It seems like on some particular setups WinUAE works like a charm, but not on one single of the setups I've tried (or my friends). So, what's the deal? Really?