Electron: hard fault reasons / explanation

Hi, sometimes after ~5h of runtime my electron runs into a hard fault -> restarts -> hard fault -> and starts to hang in this loop.
Since I am a beginner in this field my question is what exactly is a hard fault ?
Why is the automatic restart of the device not clearing it ?
And what are common reasons for this behavior ?

The most common reason for hard faults are due to code violating buffer/variable boundaries or memory leaks.

That depends on the actual cause and your code. If you have anything retained or stored in EEPROM that will be still buggy after a restart, that’s one possible reason.