I think the there is no Hour value for the hours where no production takes place, so the match fails for those bars (and returns 0).
If this indeed the problem, one possible solution would be to create a dummy production value of 0 for these hours. Or create a separate table containing all 24 hours with the same field name, Hours. A bonus of this is that you can use the load order to sort - provided you create this table before loading the production data. A simple inline load will do it:
LOAD * Inline