Getline() loops over one record in the .csv file after overwriting. What to do?

Question

C++ / C#

The program has to find a certain number in the list, and it works well exactly until overwritten and restarted. In other words, the program changes the .csv file as follows: it creates a new file, overwrites everything from the old one there, changing the required field along the way, deletes the old file and renames the new one. The names do not differ in any way, the format does not change, only 2 digits change, however, the reading code stops working after overwriting, fixating on one of them. What could be the reason?