Continuous Aggregation: next schedule run shows "-infinity"

We are running two continuous aggrigation task on our Timescale Database. Everything worked well until the second June this year. Since then there is no successful finish anymore of the task “PerDayMeasureValueStatistic”. (see Image)

The Timescale Database version is 1.7.1 (pretty old).

Does anybody now, how I can see, what is going wrong with this Continuous Aggrigation?