I have a pervasive problem where downloads of moderately sized files (> 100MB) are very slow in Firefox but fast in Chrome. When I begin downloads the speed is fine at around 4MB/s but it quickly drops down to < 200Kb/s. This happens across multiple websites and when on different WiFi networks. However when I attempt to download these same files using Google Chrome they maintain the initial 4MB/s download speed for the entire duration. I have already tried running Firefox in safe mode and resetting it using the "Refresh Firefox" help page. I am running Ubuntu 18.04.