Inaccurate measurement double load cell circuit

Question

I’m building a circuit with two load cells and I have some issues getting accurate measurements. At first I just soldered the load cells onto the load cell amplifier but as the connections seemed bad I added a wire to board terminal block to have a « cleaner » connection but that doesn’t seem to have changed anything. I built a custom PCB for the whole circuit as there is also a battery, on/off switch and an arduino. This is my first project, I’m fairly new to electronics. Please tell me if there is something I’m doing wrongly.

Schematic:

Board:

Assembled device:

This is the code I ran to get the measurements:

#include <ArduinoBLE.h>
#include <HX711_ADC.h>
​
BLEService OneRM ("xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx");
BLEFloatCharacteristic OneRMCharacteristic("xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx", BLERead | BLENotify);
​
const int HX711_dout = 3;
const int HX711_sck = 2;
​
HX711_ADC LoadCell(HX711_dout, HX711_sck);
​
unsigned long t = 0;
​
void setup() {
  Serial.begin(57600);
  delay (10);
  Serial.println();
  Serial.println("Starting...");
​
  if (!BLE.begin()) {
    Serial.println("BLE Startup Failed.");
    while (1);
  } else {
    Serial.println("BLE Startup Worked.");
  }
​
  BLE.setLocalName("OneRM");
  BLE.setAdvertisedService(OneRM);
  OneRM.addCharacteristic(OneRMCharacteristic);
  BLE.addService(OneRM);
​
  BLE.advertise();
  Serial.println("Bluetooth device active, waiting for connections...");
​
  LoadCell.begin();
  float calibrationValue;
  calibrationValue = -50;
​
  unsigned long stabilizingtime = 2000;
  boolean _tare = true;
  LoadCell.start(stabilizingtime, _tare);
  if (LoadCell.getTareTimeoutFlag()) {
    Serial.println("Timeout, check MCU>HX711 wiring and pin designations");
    while (1);
  } else {
    LoadCell.setCalFactor(calibrationValue);
    Serial.println("Startup is complete");
  }
}
​
void loop() {
​
  static boolean newDataReady = 0;
  const int serialPrintInterval = 0;
​
  BLEDevice central = BLE.central();
​
  if (central) {
    Serial.print("Connected to central: ");
    Serial.println(central.address());
    while (central.connected()) {
      if (LoadCell.update()) newDataReady = true;
      if (newDataReady) {
        if (millis() > t + serialPrintInterval) {
          float i = LoadCell.getData();
          Serial.print("Load_cell output val: ");
          Serial.println(i);
          OneRMCharacteristic.writeValue(i);
          newDataReady = 0;
          t = millis();
        }
      }
​
      if (Serial.available() > 0) {
        char inByte = Serial.read();
        if (inByte == 't') LoadCell.tare();
      }
​
      if (LoadCell.getTareStatus() == true) {
        Serial.println("Tare complete");
      }
    }
​
    Serial.print(F("Disconnected from central: "));
    Serial.println(central.address());
  }
}