What may be the cause of pinching pain in the chest?

Hello doctor,

I am writing this query for my father. He is 62 years old. He has BP and sugar but both are very much in control. He gets a slight pinching like pain on left chest and rarely on right chest. It stays only for few seconds. In a day, it comes like five to six times for every three to four weeks. We took ECG and I am attaching the file. Our general physician says that it is normal but in the ECG it is mentioned as undefined abnormal ECG. It says flat T and left axis deviation (please refer the file). Our physician says it is nothing to worry about. He says the pain is because of gastric problem. My dad goes for walking every day. He walks for 45 mins and covers four km. Our doctor says if the heart has any problem, then one cannot walk that much. Kindly refer the attached ECG and please explain if there is any problem. Kindly explain the reason for flat T and if it is something to worry about.