We have a design with 3 THS4521 into an ADS1274, and we are seeing a digital shift in signal on about 3% of our production boards. We have not been able to narrow down the cause. I've posted with this a schematic we've used for simulation for one channel, and raw samples plotted showing the issue. The red channel is the one having the level shifts, and we have seen it have more than one level it shifts between. It is not consistent which channel has the issue, as other boards have had the issue on the blue channel (the high frequency noise on the blue channel is from testing with open boards). We've tried replacing the diff op amp multiple times, replaced capacitors, taken from one channel to another, wired over from power and ground of other channels, and we still cannot find out the cause of the discontinuities. The shifts cause low frequency noise, and our application uses frequencies from 0.4 Hz to 2 kHz. We have found that heat via a soldering iron on the pins of the part cause the issue to happen more consistently for a while, with it getting better over time, but still intermittently happening.
Any help would be appreciated.