Hi Dan,
since you are an advanced user, I am a little bit sad about you luck with the Zauri. I remember you have problems with both.
Have you ever flashed a newer sharprom on the Z with screenlight problems. The Sharprom flashes different and update also deeper code like the bootloader. This is the reason they have another flash concept, just with one file called OSPACK.
If you even flashed one, maybe files corrupted while download. Maybe flashing an OSPACK which is checked after download, I dunno if the sharp people use md5 check, could solve your problems. After that you can flash OZ again, since OZ does nothing with that deeper code.
I also remember some people had problems with touchscreen (not depending to specific rom). Maybe search the forum.
Cheers,
Sam