We having problems with 95% billing with 2 ports. The graphs are just fine but the 95% percentile value keeps being 0 bpps. 
billing-calculate.php shows:

12/01/13 @ 00:00:00 to 12/31/13 @ 23:59:59 CDR      90Mbps     0bps       0% Updated!  Updated history!

Today I upgraded to latest revision but does not fix it either. Other customers are working fine but they do not have combined/multiple
links in the billing module.