Time series missing in PMM

I am using the textfile collector to feed several application metrics to PMM - which worked just fine.
Today I realized that some of the time series for all of the metrics in the text file are missing in PMM.

Here is (part of) an example metric:

envi_errors_total{worker_group=“aggregator”,worker=“envi-test-2-aggregator-2”,envi=“envi-test-2”} 0
envi_errors_total{worker_group=“aggregator”,worker=“envi-test-2-aggregator-1”,envi=“envi-test-2”} 0
envi_errors_total{worker_group=“data-quality-handler”,worker=“envi-test-2-data-quality-handler-1”,envi=“envi-test-2”} 1188
envi_errors_total{worker_group=“maintenance-job-handler”,worker=“wda-dev-maintenance-job-handler”,envi=“envi-test-2”} 0
envi_errors_total{worker_group=“maintenance-job”,worker=“envi-test-2-maintenance-job-1”,envi=“envi-test-2”} 0
envi_errors_total{worker_group=“logger”,worker=“envi-test-2-logger-1”,envi=“envi-test-2”} 7951

The two entries with label worker_group=“maintenance-job-handler” and “maintenance-job” are missing in PMM.
Adding new entries or changing existing ones (e.g. just by adding “-test” to the label value) is working fine - the values then can be found in PMM, so the cardinality limiter does not seem to be causing this.

The VictoriaMetrics Dashboards look fine, I also cannot see a related error message in the victoriametrics.log. There is also no pmm-agent error message on the client node.
PMM server and PMM client are both version 2.25.

I assume that there is either an issue with the VictoriaMetrics database or the textfile collector, but how to dig deeper into this?

Thanks for your support,
Rainer