OH2: SUM for all open/closed Rollershutters?

I have another difference since moving from OH1 to OH2:
SUM does not seem to work correctly anymore.
My items file:
Group:Rollershutter:SUM gRollershutter “Rollos [%d/5 zu]”
My sitemap file:
Frame label=“Gruppen”
Switch item=gRollershutter mappings=[UP=“Auf”, STOP=“X”, DOWN=“Zu”]

I am using Z-Wave Fibaro FGR-222, but that shouldn’t matter, right?
The rollershutters can only have the state 0% (displayed as 1%, see other thread) and 100%, no intermediate value.
I get different displays, from “Rollos 2/5 zu” to “Rollos 100/5 zu”.
In OH1, this correctly indicated “Rollos 0/5 zu” … “Rollos 5/5 zu”.
This might be solved with a rule, but SUM is much more straightforward.
Any help is appreciated.

@michel53 did you find a solution?

No - but I have not searched much further.
I am now counting the open/closed shutters via rule (>1%) and set a virtual item that is displayed in the sitemap.