This is a puzzler. Rhino 8 Mac is randomly showing hidden lines in Technical Details, but only in the generated PDF. The screen image on the Layout page is OK. Annoyingly, this is a random gremlin, which sometimes self corrects. After seeing the behaviour, I switched all Technical Details to Wireframe, then immediately back to Technical. That generally allows the PDF to be generated correctly. However, after reopening Rhino, then regenerating the PDF, sometimes the problem reappears. Reopening Rhino again and regenerating the PDF sometimes resolves the problem.
I have created a new copy of the model using Finder Duplicate, but that did not help.
There are no bad objects in the model.
I have created a cut down version of the model, but I cannot get it to display the problem.
I installed an update to Rhino this morning before the problem occurred.
There are 17 layout pages. I opened the model, generated all 17 pages as individual PDF files, then generated all 17 pages as a single PDF. All 18 PDF files were correct. I closed the model without saving.
I then reopened the model and generated all 17 pages as a single PDF. All of the Technical Details showed the hidden lines. Perhaps the mix of views is causing the problem. There are Technical Details on pages 3, 4, 14, 15 and 16 of the set.
I then opened the model in Rhino for Windows on my Windows laptop. I generated all 17 pages as a single PDF. It was correct, so it is a Mac issue only.
The reason that the cut down version of the model did not demonstrate the problem is that it had only 1 layout page, with only Technical Details. I duplicated the layout and set the details on the first page to Wireframe. Now when both layouts are printed together, the Technical page shows the hidden lines. After that, when I print only the Technical page, it is correct. When I then print both pages again, both are correct.
Another work around is to open on screen all Layout pages which have Technical Details before printing. That seems to force recognition of the Technical view before the multi page print.