Solution
The PXIe-4309 is equipped with an anti-aliasing filter and a multiplexer (MUX) for channel groups.
Strain gauges need to charge the input capacitance of the amplifiers as the inputs switch. For example, refer to the source impedance errors page in the specification document. Considering that strain gauges are generally greater than 120 ohms, this is likely the cause. The PXIe-4309 is optimized/guaranteed to work at ≤ 50 ohms and ≤ 10 S/s.
