Steps to reproduce:

1. Add host with SNMPv3 to monitor Dell iDrac through Zabbix proxy.
2. Set "Refresh unsupported items" to 60s.
3. After a variable period, SNMP is unvailable and display "Timeout while connecting to <ipaddress>"
4. Clone this host, change only name (in my case, add -clone), all other value keep the same.
5. The clone work perfectly, but after a variable period, the problem appear again.
6. Disable and re-enable host fix issue, but after a period, the problem appear again also.
7. Increase debug level. Host with timeout never appear in log. Clone host without problem appear (log output in the Result section below) :

Result:

{{ }}_{1479:20191211:142644.274 End of substitute_key_macros():SUCCEED data:'discovery{#MEMORYID},1.3.6.1.4.1.674.10892.5.4.1100.50.1.8.1,{#MEMORYMANUFACTURER},1.3.6.1.4.1.674.10892.5.4.1100.50.1.21.1,{#MEMORYCAPACITY},1.3.6.1.4.1.674.10892.5.4.1100.50.1.14.1,{#MEMORYPN},1.3.6.1.4.1.674.10892.5.4.1100.50.1.22.1,{#MEMORYSERIAL},1.3.6.1.4.1.674.10892.5.4.1100.50.1.23.1,{#MEMORYSPEED},1.3.6.1.4.1.674.10892.5.4.1100.50.1.15.1'
1479:20191211:142644.274 In get_values_snmp() host:'HIDDEN-ob-ing-poc-caas-esx02-clone' addr:'172.31.17.4' num:1
1479:20191211:142644.274 In zbx_snmp_open_session()
1479:20191211:142644.299 SNMPv3 [[email protected]:161]
1479:20191211:142644.299 End of zbx_snmp_open_session()
1479:20191211:142644.299 In zbx_snmp_process_discovery()
1479:20191211:142644.299 In zbx_snmp_translate() OID:'1.3.6.1.4.1.674.10892.5.4.1100.50.1.8.1'
--
1470:20191211:142714.159 End of substitute_key_macros():SUCCEED data:'1.3.6.1.4.1.674.10892.5.4.200.10.1.12.1'
1470:20191211:142714.160 In get_values_snmp() host:'HIDDEN-ob-ing-poc-caas-esx02-clone' addr:'172.31.17.4' num:16
1470:20191211:142714.160 In zbx_snmp_open_session()
1470:20191211:142714.184 SNMPv3 [[email protected]:161]
1470:20191211:142714.185 End of zbx_snmp_open_session()
1470:20191211:142714.185 In zbx_snmp_process_standard()
1470:20191211:142714.185 In zbx_snmp_translate() OID:'1.3.6.1.4.1.674.10892.5.4.700.12.1.11.1.4'
--
1469:20191211:142734.297 End of substitute_key_macros():SUCCEED data:'discovery{#MEMORYID},1.3.6.1.4.1.674.10892.5.4.1100.50.1.8.1,{#MEMORYMANUFACTURER},1.3.6.1.4.1.674.10892.5.4.1100.50.1.21.1,{#MEMORYCAPACITY},1.3.6.1.4.1.674.10892.5.4.1100.50.1.14.1,{#MEMORYPN},1.3.6.1.4.1.674.10892.5.4.1100.50.1.22.1,{#MEMORYSERIAL},1.3.6.1.4.1.674.10892.5.4.1100.50.1.23.1,{#MEMORYSPEED},1.3.6.1.4.1.674.10892.5.4.1100.50.1.15.1'
1469:20191211:142734.297 In get_values_snmp() host:'HIDDEN-ob-ing-poc-caas-esx02-clone' addr:'172.31.17.4' num:1
1469:20191211:142734.297 In zbx_snmp_open_session()
1469:20191211:142734.322 SNMPv3 [[email protected]:161]
1469:20191211:142734.322 End of zbx_snmp_open_session()
1469:20191211:142734.322 In zbx_snmp_process_discovery()
1469:20191211:142734.322 In zbx_snmp_translate() OID:'1.3.6.1.4.1.674.10892.5.4.1100.50.1.8.1'}}}{{

Expected:
When SNMP became available again, this error message disappear.