Hi,
I guess your board issue is about Power supply. If when all board running together then something happen on power related, It could be Your DC-DC converter is lack of power, we can use another higher power DC-DC converter in order to make sure power distribution was correct. And we can check the entire circuit, to make sure it's already in correct ways.
I have became PCB designer since 2012 and has done lot of PCB for various kind of application from hobbyst, robotic, industrial, IoT, and Military. Most of my project I did in eagle, so, this is my daily job.
I always following Design guide from vendor in order to make sure my board work propperly, But I can analyze circuit too, since My background is Electronic Engineering, and I'm work on that Industry. I have experience designing critical PCB design like High speed digital communication, Differential Pair, mixed signal PCB,On board antenna, Isolated I/O, BGA fan out, etc.
Let's discuss this project, as well as finding solution of your current problem over messengger.
Let me help you.
Best Regards,
Rijal