In the MIB file you are uploading it will have a line like the following near the top:
NAME-OF-MIB-HERE-MIB DEFINITIONS ::= BEGIN
On the Data Aggregator:
1) cd <DataAggregatorInstallDirectory>/apache-karaf-*.*.*/MIBDepot
grep "NAME-OF-MIB-HERE-MIB DEFINITIONS" *
3) If another file exists with the same line, remove the file from the Basic Vendor Certification UI upload dialog
before uploading the MIB file again.