Generating pdf drawings Rhino 5 & 6 differences

Hello,
i am using custom display modes in Rhino to generate technical drawings to .pdf files. Below You can find two example of using the same display mode, but generated from Rhino 5 and Rhino 6. Can someone explain, why it is looking normal in rhino 5 and in rhino 6 there are those thick lines and it is not possible to use it.
With simple drawing it is not a problem to make it in Rhino5 and generate .pdf from it, but when there is a bigger model with some .stp files imported in it (more details), rhino 5 starts to struggle and drawing loading process is taking ages.
Looking forward for You advices!
RHINO 5:

RHINO 6: