I have the following code built with Single Connection SDK and another one, with Multi Connection SDK:

I show part of the code below:
In file att.c:
// RxTx Communication
// 001b - 1e
{4,ATT_PERMISSIONS_READ, 2,2,(u8*)(&my_primaryServiceUUID), (u8*)(&my_RxTx_ServiceUUID), 0},
{0,ATT_PERMISSIONS_READ, 2, sizeof(my_RxTxCharVal),(u8*)(&my_characterUUID), (u8*)(my_RxTxCharVal), 0}, //prop
{0,ATT_PERMISSIONS_WRITE, 2,sizeof(my_RxTx_Data),(u8*)(&my_RxTxUUID), (&my_RxTx_Data), &RxTxWrite}, //value
{0,ATT_PERMISSIONS_RDWR,2,sizeof(RxTxValueInCCC),(u8*)(&clientCharacterCfgUUID), (u8*)(RxTxValueInCCC), 0}, //value

In app.c
int RxTxWrite(void * p) {
  uint8_t inData[30];
  rf_packet_att_data_t *req = (rf_packet_att_data_t*) p;
  rf_pkt_test *req1 = (rf_pkt_test*) p;
  for(int i=0; i < 20; ++i){
   inData[i] = req1->data[i];
  }
 #if UART_DEBUG
  at_print("packet 20 bytes\n";
  at_print_hexstr(inData, 20);
  at_print("req->dat 4 bytes\n");
  inData[0] = req->dat[0];
  inData[1] = req->dat[1];
  inData[2] = req->dat[2];
  inData[3] = req->dat[3];
  at_print_hexstr(inData, 4);
  at_print("\n");
  #endif
  ble_sts_t status = blc_gatt_pushHandleValueNotify(slave_connHandle,RxTx_CMD_OUT_DP_H, inData, 4);
  return 0;
}
From the phone connected to the device I sent text "test"
log result received: packet 20 bytes 07 6D C0 06 0C 6C 70 07 6F 00 80 00 04 A2 11 48 A5 A0 88 02 

req->dat 4 bytes

A2 11 48 A5

On the device with firmware built using Single Connection SDK, the received data is correct - "test"

On the device with firmware built using Multi Connection SDK, the received data is incorrect - A2 11 48 A5
I have noticed that 20 bytes in the received packet is always the same, no matter what data is sent from the phone. So the 20 bytes in the packet don't contain the received data.

What am I doing wrong?

What has changed from Single Connection SDK? It has been working fine for months without issues.