Hi San,
Incorrect/Wrong data result is not an easy issue to be found before doing some further analysis.
To confirm whether it is relevant for plan buffer, you may change the plan buffer query cache mode to inactive status(RSRT -> Multiprovider/!!1Multiprovider -> Property).
If the result is still not ok, the issue seems not relevant for plan buffer.
By the way, have you given the filter 0INFOPROV = "plan cube" in query designer?
Best Regards,
Sheldon.