actual process is when i am trying convert a lead in custom convert.after convert lead ststus set as a Custom Converted. after that i need to set record lock. so i am trying to set record lock by using the process bulider and Approval process.in that process i got this issuse.
Update failed. First exception on row 0 with id 00Q22000001F4nLEAS; first error: CANNOT_EXECUTE_FLOW_TRIGGER, The record couldn’t be saved because it failed to trigger a flow. A flow trigger failed to execute the flow with version ID 301220000000ZNe. Flow error messages: An unhandled fault has occurred in this flow
An unhandled fault has occurred while processing the flow. Please contact your system administrator for more information. Contact your administrator for help.: 
please fix this issue.
otherwise tell me how to set record lock through apex code are admin side.i know winter 17 release. but it was not support for my org. because my org is summer 16.