Can not execute Sonar: Can not add twice the same measure on [class]

This problem occurs on our system since 19th April, which is probably when we upgraded to Sonar 2.7. Only one of our projects 20+ is affected by this. I can't read much out of it, just that it seems to be the Subversion plugin involved here.

That's the log saying:

org.sonar.api.utils.SonarException: Can not add twice the same measure on [[our.java.ClassName]]:org.sonar.api.measures.Measure@2e14ee51[id=null>,metricKey=revision,metric=org.sonar.api.measures.Metric@1ba4806[key=revision,name=Revision,type=STRING,enabled=true,qualitative=false,direction=0,domain=SCM,worstValue=<null>,bestValue=<null>,optimizedBestValue=false,hidden=false],value=<null>,data=26268,description=<null>,alertStatus=<null>,alertText=<null>,tendency=<null>,date=<null>,variation1=<null>,variation2=<null>,variation3=<null>,variation4=<null>,variation5=<null>,url=<null>,characteristic=<null>,persistenceMode=FULL]
at org.sonar.batch.index.Bucket.addMeasure(Bucket.java:101)
at org.sonar.batch.index.DefaultIndex.addMeasure(DefaultIndex.java:167)
at org.sonar.batch.DefaultSensorContext.saveMeasure(DefaultSensorContext.java:120)
at org.sonar.plugins.scmactivity.ScmActivitySensor.copyPreviousFileMeasures(ScmActivitySensor.java:117)
at org.sonar.plugins.scmactivity.ScmActivitySensor.inspectFile(ScmActivitySensor.java:106)
at org.sonar.plugins.scmactivity.ScmActivitySensor.analyse(ScmActivitySensor.java:88)
at org.sonar.batch.phases.SensorsExecutor.execute(SensorsExecutor.java:59)
at org.sonar.batch.phases.Phases.execute(Phases.java:75)
at org.sonar.batch.ProjectBatch.execute(ProjectBatch.java:55)
at org.sonar.batch.Batch.analyzeModule(Batch.java:158)
at org.sonar.batch.Batch.analyzeModules(Batch.java:76)
at org.sonar.batch.Batch.execute(Batch.java:62)
at org.sonar.maven3.SonarMojo.executeBatch(SonarMojo.java:144)
at org.sonar.maven3.SonarMojo.execute(SonarMojo.java:135)
at org.codehaus.mojo.sonar.Bootstraper.executeMojo(Bootstraper.java:113)
... 23 more

Workaround happily welcomed.

Our plugins in use:
Clover 2.7
Jira 0.3
Motion Chart 1.2
SCM Activity 1.3
Structure101
Taglist 1.0
Technical Debt 1.2.1
Timeline 1.1
Useless Code Tracker 0.3