If you go to the Lifesaver website they give you a pdf explaining the issue. http://www.lifesaversystems.com/maintenance
So it seems the main issue is the virus filtering is not quite up to par.Whilst the 6000uf Bottle passed the bacteria and cyst removal testing it did not pass the virus removal testing.
NSF Protocol 231 is based on EPA guidelines of 99.99% virus removal, the virus testing returned virus removal results of between 99.9% and 99.995%. Previous test data show virus removal of 99.999%.
Whilst the difference in percentage terms between the NSF protocol 231 guidelines and the test data appears to be very small, 99.9% represents a significant decrease in the effectiveness of the virus removal properties.
In light of this information, LIFESAVER recommends that the use of the 6000uf Bottle should be immediately discontinued.
Just figured worth mentioning here for any folks who do have these filters.