The quick fix worked fine - thing is there are lots of these things about so it's not really a fix. It's still is absolutely fine in 8.6..... so I suppose OpenGL is not the answer....
Here is a single part that has the problem - ok in side / top / 3d - no good in front / back....
https://www.mediafire.com/file/ew348...rPart.zip/file
Dom