This is caused when the unpacked_data.txt file is corrupted in some manner, either not presenting the proper information or being empty. The state of the file can be confirmed by going to the Veeam catalog location which by default is C:\VBRCatalog\Index\Machines\ (your path to the VBRCatalog folder may differ). Open the unpacked_data.txt file and confirm it looks like the below. The actual time synced will very.
# Unpacked guest index data of unregistered OIBs options
# Temporary unpacked guest index data