PD or Iota for my upgrade?

I just came home from my 11 week camping trip. Dang, it was just about as hot in Zion as in Vegas. In Zion, everybody had the same idea: hike the Narrows. It's a far cry from spring time when heavy wet suits are required. Anyways, I got a lot of experience with dc/dc converters. I few months ago I also noticed the unity gain error amp and though it was quite strange. But then as you noticed, I saw the opto-isolator has an amp that may contain the gain stage. If you have a scope, I would look at the duty cycle. As the voltage drops (with high current demand), the duty cycle should increase. What's keeping the pwm pulses from increasing? Let's talk it over before you do anything drastic... As in opening up the loop to get more gain.

You may want to use a resistive load (a spool of wire in a bucket of water) to help troubleshoot. That setup is supposed to output rated current.

We'll solve the problem.

Sal