Why 2 VS 30's?

Just looking at lhr-lgw movements, noticed recently there are often 2 listings for VS30 from bgi, one a 747 one 340, at different times, why is this?

Something potentially wrong with the aircraft listings??? V-Flyers aircraft database shows the LGW-BGI outbound sectors as being served solely by a combination of LGW and LHR config 744's over the last 3 months.

The BGI-LGW return sectors show a mixture of 343's and 346's covering 9% of the last 3 months services like the LHR-LGW movements site. I cannot see that VS have had to re-position that many aircraft to cover the return sectors over a 3 month period....[?]

I think this is more likely to be errors with the logging of aircraft used...