LED Lights on Pre-lit Tree Vary in Brightness?

I have a 3 section tree with the dual LED lights, all 3 sections are lit up, however the top and bottom sections are half as bright as the middle section. I have checked the connections to make sure they are tight, if the cord gets moved the lights can flicker. It is a beautiful tree, but just looks silly dim, bright, dim. Any help?

By dkeverts