Grafana Tempo Metrics Generator stops writing span metrics after sometime

Hi ,

We are facing an issue that the tempo metrics generator initially it is working and writing the span metrics to mimir datasource. But sometimes/hours/days , the span metrics are not writing mimir datasource where the traces are sending to tempo datasources and shows the logs as spans generated. But those span metrics are not seeing in mimir datasource. Can you please let me know what could cause this issue and any workarourds for resolution.