Drilldown statements are unavailable for any assets that were allocated to a perspective group by a Cost Reallocation Rule.
Check if the assets in those perspective groups were allocated to them using Cost Reallocation Rules. By design drilldowns are unavailable for assets that were allocated to a perspective group using a Cost Reallocation Rule, because drilldowns show the data before the reallocation rule, and those assets were not in these group before the reallocation rule.