The current Android Firefox version cannot be cleared of a failed status on a file download. It survives any attempt to clear the browser, rebooting the device, or clearing the Firefox cache. It appears relaunching Firefox with this persistent status will result in the download being attempted again, with another notification of whether the download was successful or not. This can be of the utmost concern where, for example, someone might be located in a restrictive and/or monitored environment, and has attempted to download a controversial file while using a VPN. Subsequent launches of Firefox with the VPN disabled then put the request out in the open for the ISP, or government, to observe. In my opinion, correcting this bug deserves high priority.