I've just set up Herman's Calvins. One board came up at a few mV +/- and dialled straight in to 0v offset. The other dropped the current source LEDS on the - rail and took the rail down to only 13.3v. I had to dial this one right across on the trim pot on the Calvins. But then magically as it got close the rail voltage came up, the LEDS lit up, the voltage climbed to 17v and then when I dialled in the trim pot for the current source to 18v I found that the Calvins were within a few mV which dialled straight out.
There is definitely a situation where the Calvins sink so much current on one rail that the supply voltage drops out and throws everything off. It worth persevering with, I got the voltage across the 2.2r at 133mV on both sides of each board with zero offset, so it's all dialled in.
Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m