When downloading with the "always ask which folder to download to" option, Firefox used to download by default to the last folder used for download, now it seems to choose at random from any folder which is unpredictable and causes delay and incorrect download patterns. How can I return to the previous, consistent and helpful option of downloading to the last folder used by default unless i choose another folder please?
Current Firefox versions remember the download directory based upon the URL, so if the URL changes then the default folder may be chosen if there hasn't been selected a download folder before for that server.
You can disable this feature to remember the download directory via the Boolean pref browser.download.lastDir.savePerSite on the about:config page.
The browser.download.lastDir.savePerSite pref doesn't exist by default (it is a hidden pref), so you need to create it.
Create a new Boolean pref with the name browser.download.lastDir.savePerSite and set the value to false.