What does a red noodle mean?

Support Materials and Textures
1

Hi,

I have selected a number of nodes then grouped them. One of the noodles (the wire connecting nodes) has turned red - any idea what this means, please?

2

Edited… was wrong answer… Care to post image of node tree fragment?

3

Red noodles usually mean you have a cyclic dependency somewhere, ie through some path a node has its output connected to its input.