carriage return on PPT

[yangthomson]

When the cursor is located on the end of line, it does not go to the head of next new line after the enter key was pressed. Frequently, the cursor goes back to some where of the original line firstly. Then, the new line is created immediately with some characters that is the characters of the original line located at the line tail. Why it happens? How to clear the abnormal situation? Please help!!