I have a complex node setup for a material. I will add screen shots if the daily build from 16 December doesn’t work but in the meantime I am basically stopped cold until I get around this problem so I’m posting this now. In a nutshell, the output from any math node creates a red noodle somewhere along the path if that path ends up at a mix shader factor. The value I’m putting in comes out of a group node; I’ve checked it a thousand times; it is defined as type float in the group output socket. Using a value node directly does not have this problem but if the origination of the value going into the factor comes from a math (not vector math; just math) node, the red lines start showing up. I cannot be the first one to encounter this. I have used math node outputs a thousand million times and I’ve never seen this problem before. What I HAVE run across is nodes not properly resetting when there are a lot of changes to them so maybe replacing the mix shaders with new mix shaders will fix it. I will continue trying to replace nodes and see what happens but hopefully somebody knows a fix to this so I don’t have to keep taking shots in the dark. Thanks for anything that anybody can offer!