Steps to reproduce:

1. Update the zabbix-server from a lower major version to  higher one 
2. Update proxy(s) 
3. Check the data for the items monitored by server or proxy

Result:
New values collection is hanged. No overloaded processes, no high queue, and no resources lack.

Configuration cache reload -> no effect. Execute now several times -> no effect. 

Item - re-creation -> all fine. Server/proxy restart + Execute Now for the affected items -> all fine
Expected:
No hangs for data collection after the upgrade