LittleFS stops appending to files

[romix123]

Hi, I have a data logging setup using an ESP-M3 board (but also have test versions on a Wemos D1 mini).
Every hour, I write some small amount of data to a number of files on LittleFS.
The data typically is something like:
['9', 0.49],
or
['11',45433.99],
After a while, sometimes after much more than 24 hours, but typically at 6:00 in the morning, append to file suddenly stops working. I can't figure out what causes this.

void appendFile(const char * path, const char * message) {
File file = LittleFS.open(path, "a");
  if (!file) {…}
if (file.print(message)) {
    debug("Message appended: ");
  } else {
    debugln("Append failed");
  }
  delay(5000);
  file.flush();
  file.close();
}

As you can see, I have incorporated a delay, flush and close file. I even unmount and remount the entire set of log updates. Nothing seems to help. Append simply stops working after a while.
I run esp8266 3.1.1, FS is 128K
Any ideas?

[d-a-v]

You can try and run your code (and LittleFS library) on your computer and see if this bug is reproducible.
On linux, mac or windows/WSL2 with git installation of this core:

$ cd tests/host
$ make help
$ make ../../libraries/LittleFS/examples/SpeedTest/SpeedTest
$ bin32/SpeedTest/SpeedTest
[...]
==> Time to copy 65536 = 65536 bytes = 1 milliseconds = 65.54 MB/s
done
$ make path/to/your/sketch/sketch