I have an issue where my loop isnt populating the sobject from the sobject_collection on the Flow Builder (none Java version)

I have tried to prove the issue by using an Assignment 



The Loop:


then trying to pass this Loop object along:


I get an email with all the correct info in the sobject_collection etc just this error on assignment:


 

Error element Populate_Line_Items (FlowAssignment).
The flow failed to access the value for VarOppo_Line_Item_Loop.acu_prid_id__c because it hasn't been set or assigned.

An ideas?

Howdy Salesforce developers
I'm getting this error often. I'm running my batches in queue.
Any one have any idea how can we prevent this error. This error occur when Single record try to update by 2 jobs at same time.

Update failed. First exception on row 0 with id a145000000C6g5HAAR; first error: UNABLE_TO_LOCK_ROW, unable to obtain exclusive access to this record or 1 records: a145000000C6g5HAAR: []