There are two enter keys on most keyboards. The one on the numberpad is, by default, a column break rather than a paragraph break.
Some Windows laptops seem to map both of these keys together and the behavior is tied to the state of the Numlock key. If that's your problem, we can tell you how to work around that.
You are using numeric kep pad enter key which is used for column break so the subsequent text disappears and an over-set appears.
Use the enter key below the backspace for paragraph break.
To get back the text place the text cursor at the end of the paragraph and hit delete once. you will get back all the text.
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