Anne,
The datasheet for the signal conditioner says DC to 10Hz. That would be the source of the problem. You will need to get a signal conditioner that goes up the hundreds of Hz on the filtering. We have some recommendations here: https://forum.deltamotion.com/t/load-cells-and-signal-conditioners/109
We have used the Interface Force SGA here at Delta, and it has worked very well, but it isn’t easily DIN rail mountable.
-Jacob