Using QNX unix filesystem.
The files once written with good file names in a good directory and partition get corrupted in their filenames. Some of the files remain in good shape in the same directory. The bad filenames show binary code characters. Some of the filenames get all 0xff chars, like an unterminated string. Directory path remains ok. The disk media also remains good. Once re-initialized the disk space seems fine for reuse.
This happens once in a while but does happen within a couple of months time frame. The system is distributed all over the country. Only a few units return with the specific problem.
The problem gradually grows over time undetected since the file are archived data and never accessed once written. However, once the corruption of filenames start it keeps happening until the whole disk appears full. No more files can be written or deleted.
The system does continuously check and delete the oldest files once it detect the disk partition is %80 full. In the final analysis of the corrupted disk, the partition .nodes and .bitmap files are also found corrupted with all 0xff data in them. All else seems ok.