Windows 10 2004 with %temp% pointing to a ramdisk mounted with imdisk. Following the migration to version 83 the "open with" action when downloading a file won't work. The results is : In the %temp% folder a random .part that contains the correct content, also a zero byte file of the correct name. The download manager subwindow shows the file as "failed". The following possible fixes have given no positive result : Disable security software. Firefox Refresh and new profile. Change the ramdisk settings (file system type, security rights, cluster size). Only changing %temp% back to a regular drive path works but I want to keep it the way it worked with Firefox 82. Please help.