Loki filename values and job values are missing in grafana after sometime

We have installed loki using helm , and our logs are mounted on a file share, this is added in extra volume mounts , extra volumes and in extra scrape config(/mnt/azure/logs/**/*.log).Issue we are observing is the job values and filename values in grafana loki explore for the extrascrape config are missing after some time.The logs are not continuously written they are old.I really appreciate if anyone can explain why its happening.