I had a quick look at the images over your AOI and for the same dates with SNAP: the effect that you mention from one date to another with Sentinel Hub services is also visible in the images obtained directly from Copernicus with the same processing:
There are a certain number of steps applied to the S1 images that you get with Sentinel Hub: these are customisable to a certain degree. For more information see the processing chain documentation and the processing options. This will guide you on the options to select depending on what product you want.
There has already been a thread about how to get similar results with the “raw” images processed in SNAP and the Sentinel Hub products: on the SNAP forum.
Now why the noise on the 17th? Probably many different possible explanations, but you would have to dig deeper.