There is no data problem - for the timebands described there are just no counts (transactions in this case) for certain period. The data is delivered per transaction with a number of fields (e.g. timebands). If there is no transaction on, in this case, Z for a certain timeband there will simply be no line (data). However you plot dimension fields over the timebands, therefore there will be a missing symbol.
The problem is then the yellow area on the right of the image below (also shown in the example), an area is filled up while actually there shouldn't be any counts shown at all for this period (as there are none).