Question:

The fact that a label number is used more than once in a longer program is not reported in Test Run or upon selection of the program. Why?

Answer:

You can specify how far in advance the control should check for label numbers or names in the Test Run mode or after selection of a program. If the label name or number used more than once is outside of the range to be checked, the TNC does not issue an error message.

On the TNC 426 / 430 and iTNC 530 you define this range in machine parameter MP7229.0

On the TNC 128, TNC 320, TNC 620 and TNC 640 you define the range in the maxLineGeoSearch machine parameter (no. 105408) 

The greater the range you define in the parameter, the longer it will take for the TNC to begin running the program after starting it.