Reasons for system freeze without kernel panic

I have an embedded device/system with i.MX8M mini processor running on a Debian based Linux with kernel 6.12.8. If I run a specific software on that device, the system freezes only after 1-3 days of runtime. Originally the device was reset by the watchdog timer, but when disabling the watchdog, we see the "freeze" state. Yes, the watchdog functionality works OK :-) The problem **only** happens with this (rather complex) piece of software. Running other programs or software for weeks, we have never seen such a freezing (I do not have access to the source code of this software). There is no kernel fault displayed on the serial terminal, nor any kernel fault in the log files. In the freezed state, the system does not react to any connection attempt. My question: How can a user code possibly trigger such an observed system freeze state without seeing a kernel panic or anything reported by the kernel? Or the other way around: If one asks you to write a user code that freezes a Linux system completely without showing any kernel message, what code would that be?