i think it has the problem
I work on embedded processors many, many times more powerful than the Arduino, with thousands of times more memory, and dozens of separate peripherals and subsystems.
They're about the size of a credit card or smaller.
The code runs to hundreds of thousands, if not millions of lines of C, C++ and assembler (don't worry, I didn't write all of them).
Do I have an exotic JTAG debugger?
I have debug prints.
I don't "think" my code has problems - I find out.