there is a space in front of the 'E' and I assume it's null?
No. If it were the null character nothing would be printed, because Serial.println stops when it sees a null character. All C-style "string" functions stop when they see a null character, so Serial.println would stop before it started.
If there is a space before the 'E' in the output of your sketch, then there is some character in textArrayy that shows up as a space when you print it. (Maybe it's a space char, 0x20, or maybe it's some other (non-ASCII or non-printing) char that "just happens" to print out as a space...)
So why can't strncpy do it?
It can. Really.
Try the following all by itself. Then put a print statement in your sketch immediately after your strncpy statement.
strncpy(textArray, "NEW TEXT", 63);
//(later on the code)
Then: Look carefully in your sketch and see if there is a place where your program could have changed textArray.
If you didn't store something there intentionally, it's possible that writing outside the range of some other array could corrupt the contents of this array. (Or there could be bad behavior due to some misuse of a pointer variable somewhere. It's hard to say without seeing your sketch.)
It sounds more like you are appending 1 to the textArray pointer somewhere.
What do you mean "appending 1" to textArray? Do you mean adding 1? Or what?
Anyhow: textArray is the name of an array. As far as the compiler is concerned, it is a const pointer whose value is the address of the first element of the array. You couldn't increment textArray or change its value in any other way if you wanted to (or even if you didn't want to). The compiler simply won't let you.