Well, the embedded systems are wery well known for continuous fight against Universe forth dimension: time. It is known that some delays must be added inside code - this does not imply the use of a sistem delay routine always - just operation order may solve a lot.
Debugging a system with such problem is difficult. Some techniques could be used:
a) invasive ones: mark (i.e. use some printf statements) in various places of your software, entry or exit of some routines or other important steps and run again - when the application crashes, you must note the last message seen and conclude the crash is after that software step marked by the printf.
b) less invasive: use an available GPIO pin as output and set it high at the entry of some routine and low at the exit; the crasing point will leave the pin either high or low. You can use several pins if available and watch the activity with an oscilloscope.
c) non invasive - use the JTAG or SWD debugging - this is the best one - if your micro support faults debugging, then you have the methods to locate the bug.