It can happen that a function just hangs for whatever reason in between being called, but not getting into execution (rare, but shit happens).
I would advice to wrap the function into a logic app that triggers on schedule (the trigger is called
"Recurrence").
Inside the logic app you can call the function and specify detailed timeout and retry settings .
Additionally you can specify parallel following actions that run depending if the function was called successfull, failed or timed out.
This should help you reach a more stable and reliable operation and handle all kind of abnormal situations.