Not only can the jumpers on the color PCB be a source of pain on the 16, but also the ground points can come lose and cause issues, got to make sure there is no fractured solder at any on the ground points.
An issue I had with my CTC-16XL was the the orange drop capacitors near the Y-amps, these tend to get very hot and toasted and prone to failure.
shameless promo!
https://www.youtube.com/watch?v=7V3etX2NsS4