For that "stripping" I suspect some floating point rounding issues, but it might be related to z-buffer as well.
Please, can you try to run "draw zbuf" in debug console? it should render zbuffer instead of color.
I was trying to get amigaos 4.0 working with winuae & ppc qemu plugin, but i was not very lucky yet.
....maybe it will be not needed, I just did some dirty hacking, and I can get almost the same artifacts (striping on actors), looks like it related to endianes as well.
Quick update on this one about the Big Endian platforms; The z-ordering issue along with drawing issues for images should be fixed in commits by peterkohaut (since a few days now actually), so please test and verify if you are on one of such platforms. And also report any other issues you've encountered