### Description

Hi, I'm running some tests on top of Kamailio 5.3.5 (x86_64/linux) 9e70e8 on CentOS with ~1.2k registered endpoints. While I try to dump registered contacts it fails: ``` [root@v0p1356-dispatcher kamailio]# kamcmd ul.dump error: 500 - Internal error creating aor struct [root@v0p1356-dispatcher kamailio]# kamcmd ul.db_contacts location 1172 [root@v0p1356-dispatcher kamailio]# ```

### Troubleshooting

I'm running kamailio with -m 512 -M 128 and like suggested in #1513 I've tuned ctl module settings but no luck ``` modparam("ctl", "binrpc_buffer_size", 4096) modparam("ctl", "binrpc_max_body_size", 16)

```

#### Reproduction

send >1000 registrations

#### Log Messages

``` Jul 28 15:12:13 localhost /usr/sbin/kamailio[55179]: ERROR: ctl [binrpc_run.c:1094]: rpc_struct_add(): failed to add attribute-value ({) ```

### Additional Information

``` [root@v0p1356-dispatcher kamailio]# kamailio -v version: kamailio 5.3.5 (x86_64/linux) 9e70e8 flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: 9e70e8 compiled on 14:35:46 Jun 22 2020 with gcc 4.8.5 [root@v0p1356-dispatcher kamailio]#

```

* **Operating System**:

``` Operating System: CentOS Linux 7 (Core) CPE OS Name: cpe:/o:centos:centos:7 Kernel: Linux 3.10.0-1127.el7.x86_64 Architecture: x86-64 ```