Steps to reproduce:

1. Add Opengear device with SNMPv3 interface and one item to check SNMP availability.
2. Wait or "Execute item" from Zabbix frontend.

Result:

1. 1277296:20211027:142127.795 In get_values_snmp() host:'a-cm03.a.com' addr:'10.216.216.167' num:1
   1277296:20211027:142127.795 In zbx_snmp_open_session()
   1277296:20211027:142127.816 SNMPv3 [[email protected]:161]
   1277296:20211027:142127.816 End of zbx_snmp_open_session()
   1277296:20211027:142127.816 In zbx_snmp_process_standard()
   1277296:20211027:142127.816 In zbx_snmp_translate() OID:'1.3.6.1.2.1.1.3.0'
   1277296:20211027:142127.816 End of zbx_snmp_translate() oid_translated:'1.3.6.1.2.1.1.3.0'
   1277296:20211027:142127.816 In zbx_snmp_get_values() num:1 level:0
   1277296:20211027:142227.875 zbx_snmp_get_values() snmp_synch_response() status:2 s_snmp_errno:-24 errstat:-1 mapping_num:1
   1277296:20211027:142227.875 End of zbx_snmp_get_values():NETWORK_ERROR
   1277296:20211027:142227.875 End of zbx_snmp_process_standard():NETWORK_ERROR
   1277296:20211027:142227.875 In zbx_snmp_close_session()
   1277296:20211027:142227.875 End of zbx_snmp_close_session()
   1277296:20211027:142227.875 getting SNMP values failed: Timeout while connecting to "10.216.216.167:161".
   1277296:20211027:142227.875 End of get_values_snmp()
   1277296:20211027:142227.875 In zbx_deactivate_item_interface() interfaceid:52883 itemid:1397825 type:20
   1277296:20211027:142227.875 zbx_deactivate_item_interface() errors_from:1635283043 available:2
   1277296:20211027:142227.875 End of zbx_deactivate_item_interface()

1. 
2. But the host is available when checking with snmpwark from the zabbix-proxy console

[root@zabbix-proxy-01 ~]# time snmpwalk -On -v 3 -r 0 -t 30 -a MD5 -l authPriv -u nnm-switches -A q1w2e3r4 -x DES -X w2e3r4t5 10.216.216.167 1.3.6.1.2.1.1.3.0
.1.3.6.1.2.1.1.3.0 = Timeticks: (60699381) 7 days, 0:36:33.81

real    0m0.032s
user    0m0.025s
sys     0m0.003s

1. Also item successfully receives a response when checking with Test in the Zabbix frontend.

Expected:
SNMP item receives value and SNMP interface available.