Yup, same here, mostly red and towards the beginning. I noticed something over the weekend on what causes the red to "burn out". I just received another batch of 8 strings that I ordered and plugged them in for 2 hours directly to 12v. There wasn't a single bad node, so I thought great, these are perfect. After hooking them all up outside, throwing a dsc on them, I immediately had problems. Some of the reds flickered for a couple minutes and then went out. I assume this has something to do with the pwm - those bad reds don't like to be turned on and off a lot.
The moral of the story - make sure you leave your lights flashing when you burn them in. Leaving them on for a couple hours isn't enough.
I don't have time this year to take them down and splice out all the bad nodes, so I'm thinking of covering the bad ones up with black gorrilla tape so they're not visible.