Steps to reproduce:

1. Create host with SNMPv1 interface and SNMP checks.
2. Update host SNMP interface from v1 to v2 without updating new not mandatory field "Max repetition count".
3. Get error.

Result:

Expected:
Update host without entering value for "Max repetition count", by using default (10) value for it.

BTW:

1. If value provided, then host updates successfully.
2. Also this occurs in API, but in documented API method hostinterface/object "Max repetition count" is not presented. (will be nice to use default value).