This indicates a USB connection issue or outdated tool. Use the Legacy iOS Kit, as it handles these errors better than iTunes.
There are two primary ways to downgrade an iPhone 4s to iOS 5: the classic method using RedSn0w and the modern, all-in-one solution using Legacy iOS Kit. downgrade iphone 4s to ios 5
While iOS 5.0 and 5.0.1 exist, 5.1.1 is the most stable and compatible version for the iPhone 4S. This indicates a USB connection issue or outdated tool
Before you start, it's crucial to understand the implications and prepare your device: downgrade iphone 4s to ios 5