Constituent Lookup ID not entered as defined by configuration

We have a situation where a handful of constituents were entered with a lookup id that does not align with our configuration setting. This happened with a constituent update batch filled from a Zuri Velocity process. I am not seeing anything that determines the format to use when I look at the batch template or the batch commit forms and the related handlers. Does anyone happen to know how a lookupid gets entered from that batch when there is no lookupid provided to the batch? I am aware of the configuration form for this specific entity and it is set up correctly since it only happened to about 28 out of several thousand people. Is there code that determines how that lookupid is formatted in batch commit?