We've identified this to be a bug in version 4.3, when collapsing Time Entries or Expenses and none of them are flagged as Taxable.
A fix for this issue will be included in version 4.4.
As a temporary workaround until version 4.4 is available, the Taxable column on the invoices can be disabled from the Company's Export Settings.
Thank you Kaye for reporting this issue.
Ernesto.