"This is about the previous message i have recently posted."

It would've been better to continue there, rather than start a new thread.

"About the hardware, i use simple chips..."

Simple circuits can still exhibit obscure problems!

"the circuit works with all the projects i have done, except with this one"

Just because none of your previous projects found a problem is no guarantee that there is no problem!

I think it's Erik that likes to say that testing does not prove the absence of bugs (I'm sure he'll give the correct quote...)

"I have only 2 interrupt routines"

But your processor has more than 2 interrupt inputs!
As I said before, you should have an ISR for every possible interrupt source - then you can insert some debug code, or set a breakpoint to see if you're suffering from unexpected interrupts (which is certainly something that a simulator won't show you!)

"Another possibilty my professor told me, is the length of characters i used for call labels."

Nonsense, I'm afraid - unless, perhaps, you're using BASIC?
With an assembler or compiler, the labels are only used by the assembler/compiler during the translation process - they do not appear in the executable code!
An invalid label name would cause the translation to fail (it should give an error message), but cannot affect the code when it's running.

"How many characters are allowed max?"

To know that, you will have to read the Manual for the tools you're using.
You haven't told us what tools you're using, so we can't possibly answer that!