RM57L843: LwIP 1.4.1 stop working

struct tcp_pcb* conn_pcb=NULL;
err_t recv_callback(void *arg, struct tcp_pcb *tpcb,
                               struct pbuf *p, err_t err) {
	struct pbuf *pre_p = p;
	LWIP_UNUSED_ARG(err);

    /* do not read the packet if we are not in ESTABLISHED state */
    if (!p) {
        conn_pcb = NULL;
        tcp_recv(tpcb, NULL);
        tcp_sent(tpcb, NULL);
        tcp_err(tpcb, NULL);
        tcp_close(tpcb);
        return ERR_OK;
    }

    /* indicate that the packet has been received */
	do{
        // check if received data is under analysis
        if(rcvAnaFlg == 0){

          // receive buffer
            memcpy(&crxWlDtwk[cwlrxw.RxCnt], p->payload, p->len);

            // update received data count
            cwlrxw.RxCnt = (cwlrxw.RxCnt + p->len) % WL_BUF_SZ;
        }
        else{
            // skip if received data is under analysis
            testFlg++;
        }
        if(p->next==NULL) break;
		p=p->next;
	}while(p->len != 0);
 
    tcp_recved(tpcb, pre_p->tot_len); // all data received
    
    /* free the received pbuf */
	pbuf_free(pre_p);

    return ERR_OK;
}

u8_t sndWl_complete=1; //tcpSend256 completion flag
err_t sent_callback(void *arg, struct tcp_pcb *tpcb, u16_t len) {
	if(len>=256)
	{
		sndWl_complete = 1;
	}
    else{
// check if len<256
		sndWl_complete = 0;	// never comes here. len must be 256 or bigger.
    }

    return (ERR_OK);
}

err_t tcpSend256(const void *buf)
{
	err_t t_err;
	u16_t send_bufs;

	if(conn_pcb == NULL) return ERR_CONN;

	while(1){
		send_bufs = tcp_sndbuf(conn_pcb);
		if(send_bufs < 256){
			continue;  // wait until tcp transmit buffer gets 256byte
		}

		t_err = tcp_write(conn_pcb, buf, 256, TCP_WRITE_FLAG_COPY);
		if (t_err != ERR_OK) return t_err;
		t_err = tcp_output(conn_pcb);
		if (t_err != ERR_OK) return t_err;

		sndWl_complete = 0;

		break;
	}
}