If you go through and take a look at the filter and pick all and bills this will show where the difference lies, check which fee earner could of had the difference in WIP that went through on the bill by looking at the minus and positive amounts per fee earner.
The bill can then be reversed if this is something that is just a reversal time line that was done and the original was not included in the bill.
If that doesn't work the support team will need to correct.
Please raise a new case online and reference the title of this article.