Exactly how do you expect someone to find a bug in your program just because you have said that the program is written in C?

My car is a Volvo. If I claimed that there was something wrong with it, would "Volvo" be enough for you to figure out if the error is with the breaks, the engine, a flat tire, a dented bumper, ...?

If you can't post the code, then you will have to post the algorithm that describes - step by step - what your broken C program does.

And you didn't answer my questions about what is different in your program when it processes the first tag ID and when it tries to process following tag IDs. If you don't spend time making sure that all required variables gets restored to the expected values between each iteration of the code, and you don't post any other information about the code - or the code itself - you can't expect to receive any help with your problem.

We just can't guess what you are thinking just now, just as we can't guess what you ate for breakfast or the color of your clothes. All information we have is the information you post. And you are not really posting any information related to your problem.

9600 baud is obviously not an important fact, since the baudrate does work for the first tag ID. Or do you suspect that your program is switching to a different seiral speed after sending the first tag ID?