Lead convert fail when there is Lead (Process builder) trying to update the lead during the conversion.
|Knowledge Article Number||000232516|
|Description||If you have a process created for the Lead object in the process builder, you may encounter an error similar to the one below when trying to convert a lead.
"Error: System.DmlException: Update failed. First exception on row 0 with id XXXXXXXXXXXXXXX; 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 XXXXXXXXXXXXX. Contact your administrator for help.:  Class.leadconvert.BulkLeadConvert.updateLead: line 1375, column 1 Class.leadconvert.BulkLeadConvert.convertLead: line 151, column 1"
This will happen if the process you have created for leads is trying to update the lead when it's converted. When a lead is converted, some values on the lead are updated automatically and therefore, if the process is set to start "when a record is created or edited" and the criteria on is met, the process will try to update the lead after being converted, which is not possible.
|Resolution||An easy way to avoid this is adding a criteria to the process to check if lead.IsConverted is Equals False and only make updates when the lead is not being converted.|