Security settings had nothing to do with my issue. The separate processes tickbox change didn't seem to catch without a machine/program reboot. I do not know which. P11 running side by side with P12 doesn't have the same problem when using progressive rendering.

I told the install to pick up my existing settings from P11. It did and installed just fine. Both P11 installations have the separate processes tickbox checked and work just fine. P12 installed with the box checked. That was taken from my existing preferences upon upgrade and is as expected. That is what caused my progressive render, stopped early; from displaying as it used to. I checked again before replying to this post.

It is the seperate process tick box being checked in P12 that causes the issue (in my case). It does not cause this issue using P11 on the same hardware rendering the same pz3. There is a change somewhere but I don't care. Possibly with the loss of some 32 bit code in the program itself.