Amount format mistake rejects line in data load without warning or error

We have often incorrect data that users try to uplaod. This case, it was an amount with a space inbetween the minus and the value "- 123" instead of "-123". When loaded into data exchange, the system reject this line but loaded the rest. There was no error or warning displayed.

Error: [TC] - [Amount=NN]

-Is there a way to block this?
-How can we prevent this in the future?

Thanks!