I am using 22nF at moment.
Adding C8 fixed oscillations. Added two more boards, to 5 total, and will see how it goes in few days.
Just for reference note here:
Channel 2 - Rev B01 PCB, LTZ1000CH, LTC2057, 12K/1K heater - 7.1304749 VDC reference, 5ppm span on graph
Channel 3 - Rev A01 PCB, LTZ1000ACH, LTC2057, 13K/1K heater - 7.1367946 VDC reference, 5ppm span on graph
Channel 4 - Rev B01 PCB, LTZ1000ACH, LTC2057, 13K/1K heater - 7.1585775 VDC reference, 5ppm span on graph
Channel 5 - Rev A01 PCB, LTZ1000ACH, LT1097, 13K/1K heater - 7.1366038 VDC reference, 5ppm span on graph
Channel 6 - Rev A01 PCB, LTZ1000CH, LTC2057, 12K/1K heater - 7.1296732 VDC reference, 5ppm span on graph