Yesterday and today I have experienced the exact same thing. My upload goes from 0.1 Mbps to 0.5 Mbps. I work from home and these dips make it impossible to work with any files on our network. I pay for the 150 Mbps down, and "up to" 10 Mbps up, but I feel like it should be more than that.
I chatted with support earlier and they reset my modem (which I had already done) had me reset my router (which I had already done) had me connect directly to the modem with my laptop (which I had already done) and finished the chat by pushing me off to my equipment manufacturer (my modem is less than a year old).
What do I have to do to get an answer on this? Anyone have any luck?