Using Mondrian 4.0.0-SNAPSHOT (via Saiku's saiku-server) I have a Mondrian 4 schema including the following elements:

<CalculatedMember name=“Sales last year”

<CalculatedMember name=“weeks2015_sofar”

<NamedSet name=“weeks2015”>
{[Time].[2015].[1] : CurrentDateMember([Time].[Y-W], ‘[Time]\.[Y-W]\.[yyyy]\.[ww]')}


When running the following mdx query

NON EMPTY {[Measures].[Sales], [Measures].[Sales last year]} ON COLUMNS,
NON EMPTY {weeks2015, weeks2015_sofar} ON ROWS
FROM [Sales]

I get a Mondrian excpetion: MondrianException: Mondrian Error:Internal error: member [Time].[Y-W].[weeks2015_sofar not found among its siblings.

Here is the relevant snippet from the log:
Caused by: mondrian.olap.MondrianException: Mondrian Error:Internal error: member [Time].[Y-W].[weeks2015_sofar] not found among its siblings
10532 at mondrian.resource.MondrianResource$_Def0.ex(
10533 at mondrian.olap.Util.newInternal(
10534 at mondrian.rolap.SmartMemberReader$SiblingIterator.<init>(
10535 at mondrian.rolap.SmartMemberReader.getLeadMember(
10536 at mondrian.rolap.RolapSchemaReader.getLeadMember(
10537 at mondrian.olap.DelegatingSchemaReader.getLeadMember(
10538 at
10539 at$1.evaluateMember(
10540 at mondrian.calc.impl.MemberArrayValueCalc.evaluate(
10541 at mondrian.rolap.RolapEvaluator.evaluateCurrent(
10542 at mondrian.rolap.RolapResult.executeStripe(
10543 at mondrian.rolap.RolapResult.executeStripe(
10544 at mondrian.rolap.RolapResult.executeStripe(
10545 at mondrian.rolap.RolapResult.executeBody(
10546 at mondrian.rolap.RolapResult.<init>(
10547 at mondrian.rolap.RolapConnection.executeInternal(
10548 ... 7 more

When I don't use measures like [Measures].[Sales last year] using parallelperiod but only "regular" measures, I have no errors.
IS there a way to redefine the schma to avoid this and still be able to obtain column sums on the bottom for all measures?