I am trying to update multiple records using a flow. I have bulkified the update. Update is using a collection to update records. The mentioned collection stores Record Ids. But it gives the following error:

Error Occurred:
The flow tried to update these records: a035i000001fWhgAAE. This error occurred: CANNOT_EXECUTE_FLOW_TRIGGER: We can't save this record because the “AutoSeq1” process failed. Give your Salesforce admin these details. 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.

It occurs only when multiple records are being updated. Is there something that is missing? How can this error be handled?

Whenever we try to import the data having a master-detail relationship or a lookup relationship using the following query

sfdx force:data:tree:export -q "query to fetch child data with master table attribute in select statement" -d ./data

the data gets stored in json format under data folder. But the reference to the parent or the lookup relationship is not fetched or stored. Is there a way to import all the data without losing the referencing?