Steps to reproduce:

1. Open Data collection -> Templates
2. Find a template with extended value mapping, for example: Cisco Catalyst 3750V2-24FS by SNMP
3. Open the template
4. Click clone

Result:
Create new template form is displayed with no data.
See video:

Note: if the mapping "IF-MIB::ifType" is removed, cloning the template is working as expected.

Expected:
Cloned template form should be displayed.