Disk full truncates log records

An append-only event log service writes newline-delimited JSON records to a local segment file, then a separate compactor ships sealed segments to object storage. At 02:40 the host's data disk briefly hit 100% (a runaway log filled it, then logrotate freed it 6 minutes later). No process crashed. This morning a downstream consumer reports ~0.05% of records fail to parse, and a few that do parse have a truncated tail field merged into the next record's first field. Dashboards: write success rate was 100% the whole time (the writer treats a short write as success), disk now at 60%. How do you triage, stop the bad segments from propagating, and recover the data?