When your table has more than 1 field with relations to sys_category you will run into problems because the MM relation table sys_category_record_mm will only store which table a category belongs to - but not the specific field.
You need to extend sys_category_record_mm like this:
Add the following to your extension's ext_tables.sql:
CREATE TABLE sys_category_record_mm (
| // This file must be imported before loading html5-boilerplate | |
| // Imports ------------------------------------------------------------------- | |
| @import "compass/css3"; | |
| @import "compass/typography/vertical_rhythm"; | |
| // Grid (http://susy.oddbird.net/) ----------------------------------------------------- | |
| // | |
| @import "susy"; |
| <div class="itemsListYearMonth"> | |
| <a:groupedForDateTime each="{items}" as="itemsByYear" groupBy="start" format="Y" groupKey="year"> | |
| <a:groupedForDateTime each="{itemsByYear}" as="itemsByMonth" groupBy="start" format="m" dateTimeKey="month"> | |
| <div class="yearMonth clearfix"> | |
| <div class="timeframe" data-behavior="FixTimeframe"> | |
| {month -> f:format.date(format: 'F Y')} | |
| </div> | |
| <f:for each="{itemsByMonth}" as="item"> | |
| <div class="item"> | |
| <p class="startEnd"><a:format.duration start="{item.start}" end="{item.end}" /></p> |
