Triplicated AWS Managed Grafana alerts using SNS

Hi everyone!

We have a AWS Managed Grafana alert connected to AWS Timestream:

The alert fires a SNS notification (which is processed by a lambda function) and an email. The problem is, we keep receiving always 3 notifications, with the same valueString. For example, here are 3 valuesStrings which came in 3 different notifications:

[ metric='_col1' labels={serial_device=158857075025556} value=-17.558333333333334 ], [ metric='_col1' labels={serial_device=132400469686384} value=-16.96666666666667 ], [ metric='_col1' labels={serial_device=246326151756948} value=-19.638461538461538 ], [ metric='_col1' labels={serial_device=27418224420500} value=-15.080000000000005 ]

[ metric='_col1' labels={serial_device=27418224420500} value=-15.080000000000005 ], [ metric='_col1' labels={serial_device=132400469686384} value=-16.96666666666667 ], [ metric='_col1' labels={serial_device=246326151756948} value=-19.638461538461538 ], [ metric='_col1' labels={serial_device=158857075025556} value=-17.558333333333334 ]

[ metric='_col1' labels={serial_device=158857075025556} value=-17.558333333333334 ], [ metric='_col1' labels={serial_device=246326151756948} value=-19.638461538461538 ], [ metric='_col1' labels={serial_device=132400469686384} value=-16.96666666666667 ], [ metric='_col1' labels={serial_device=27418224420500} value=-15.080000000000005 ]

We also tested Reduce followed by Math expressions, instead of Classic Condition, but the problem remains.