Both frequency and symbol rate can vary from receiver (and LNB) to receiver (and LNB). Usually, it is better to do a blind scan rather than a manual entry. That way your receiver and LNB (both of which can affect the Freq. and SR numbers) can find the numbers that it can lock in the signal. Frequency can be plus or minus 2 or 3 (and symbol rate can also vary by that much or more) without any cause for alarm.
I am surprised that a difference between 11575 and 11574 would make such as difference, as usually the SR is one of the more flexible of the two numbers. It could be that your receiver would have scanned in the transponder at a lower SR (say 11572), and couldn't compensate. I have two receivers connected to the same LNB and one scans it in at 11573, and the other at 11574.
