Issues when using MPI_Win_create() and MPI_Get() functions

Question

In MPI (MPICH) I am trying to use windows. I have a 3D grid topology and additional communicator i_comm.

  MPI_Comm cartcomm;
  int periods[3]={1,1,1}, reorder=0, coords[3];
  int dims[3]={mesh, mesh, mesh};  //mesh is size of each dimention
  MPI_Dims_create(size, 3, dims);
  MPI_Cart_create(MPI_COMM_WORLD, 3, dims, periods,reorder, &cartcomm);
  MPI_Cart_coords(cartcomm, my_rank, 3, coords);

  MPI_Comm i_comm;
  int i_remain_dims[3] = {false, true, false};
  MPI_Cart_sub(cartcomm, i_remain_dims, &i_comm);
  int i_rank;
  MPI_Comm_rank(i_comm, &i_rank);

  MPI_Win win_PB;

  int * PA = (int *) malloc(r*r*sizeof(int)); //r is input size 
  int * PB = (int *) malloc(r*r*sizeof(int));

  /* arrays are initialized*/

Then I create window and afterwards try to use get function

  if(i_rank == 0){
      MPI_Win_create(PB, r*r*sizeof(int), sizeof(int), MPI_INFO_NULL, i_comm, &win_PB);
    }
  else{
      MPI_Win_create(NULL, 0, 1, MPI_INFO_NULL, i_comm, &win_PB);
    }

  MPI_Win_fence(0, win_PB);
  if(i_rank != 0){
      MPI_Get(PB, r*r*sizeof(int), MPI_INT, 0, 0, r*r*sizeof(int), MPI_INT, win_PB);
  }
  MPI_Win_fence(0, win_PB);

With this code I get long output of errors:

[ana:24006] *** Process received signal ***
[ana:24006] Signal: Segmentation fault (11)
[ana:24006] Signal code: Address not mapped (1)
[ana:24006] Failing at address: 0xa8

Also, without using MPI_Win_fence, I get error with get function: MPI_ERR_RMA_SYNC: error executing rma sync. Which I am not sure is normal.

What I observed is that if I declare arrays in a reverse order then it works fine:

int * PB = (int *) malloc(r*r*sizeof(int)); 
int * PA = (int *) malloc(r*r*sizeof(int));

The problem is that I will need to create another communicator and another window for PA buffer, so just switching order of lines does not help at the end.

I would highly appreciate any help to figure out what I am doing wrong.