Debian wifi performance

I’m using the debian images from here: on the DB410c and I notice the wifi network speed is very fast at first but rapidly degrades to less than 100kB/s and stays there. If I use a use wired ethernet adapter it runs at the network speed. Is there a known issue using the onboard wireless with the 4.9 kernel? My wireless mouse also gets disconnected when the transfer speed is high at the start, so possibly the radio is not tuned properly? I have observed it at home (very little radio interference) and at the office, so it’s probably not environmental.

Edit: Tried on the jesse image, it behaves the same.