I didn't notice what and when happend but from some moment replacing stopped work in Word.

Just imagine that I have a text block:

Some text block

And I select the word text:

Some text block

After that I press some key, for example, 'A'. And I expect to see

Some A block

because selected area should be replaced (as usual).

But instead of that I see:

Some Atext block

Inserted text is just appended as prefix.

Could anyone help me with this issue, please?