First of all, you aren't using "pieces" as the variable, but "<var:minigame:pieces>" as in <var:minigame:<var:minigame:pieces>>
You only need to use <var:...> when using ifValue or in text, not when using ifVariable or ModVariable
Maybe using that can be the cause, but I don't think it is something game breaking.
Secondly, I may be wrong here but I think in line 10 of your win brick you need to change the number in the sub box from "11" to "11 11"
It needs 2 variable, starting and stopping. Just placing one may not be integrated in VCE.
What I think may fix the problem is adding 1ms delay on line 8 of your win brick.
I think after executing the win event it stops executing other events. Adding that delay will make sure it goes in the right order.