Sorry to post on this old thread. I was searching for this issue on Google and this is the first result, so might as well add some useful info I found. This happens for Cura on a large network (school) in our case and it was annoying to have to turn off WiFi everytime we used Cura. We found that the issue was fixed not only by turning off the OctoPrint plugin but also by turning off the UM3 Network Connection plugin. After that, Cura showed the same speeds that would happen while disconnected from the network.