Hi Amit,
if it's happening only intermittently, it is very likely that it was caused by some connection problem. However, once the function modules and the used data types are cached by the NCo runtime, it's actually no longer necessary to look them up unless your code regularly clears the repository. Or the program itself is only a short-runner ...
In order to find the real cause, the log would be helpful and if it's possible to run with trace turned on for a longer time a trace at level 4 of this situation.
Best regards,
Markus