Hmm well the report of a failure. I did this DC lab amp. 1st stage is an INA121. The way the front panel was arranged I could not fit my Int amp symmetric with the inputs. Big mistake!, my one side (+ in this case) see's a lot more stray capacitance. At least that's my first idea. High impedance, stray C. Duh, (As long as each side is 'equally weird' at the high gain end, I don't mind as much.) (I've got two x1k gain stages in series, I always thought that might be a tad too much.) (oh a LP filter and DC offset in between, gain on both ends The filters are switched R in to C, with a buffer/ follower.
I think rotating the toggle switches will fix things. (the art work has to change...NBD.)