Any ways to get around the download failing

I did this incredibly stupid procedure with Firefox yesterday as a workaround for a failing Google Takeout download:

• backup the .part file from the failed download
• restart the download (careful -- if you didn't move/back it up, it will be deleted and you will have to download the whole thing again; found this out the hard way on a 50GB+ file... that failed again)
• immediately pause the new download after it starts writing to disk
• replace the new .part file with the old .part file from earlier (or -- see [1] below)
• Firefox might not show progress for a long time, but will eventually continue the download (I saw it reading the file back from disk with iotop so I just let it run)
• sanity check that you actually got the whole thing and that it is usable (in my case, I knew a hash for the file)

[1] You can actually replace the new .part file with anything that has the same size in bytes as the old file -- I replaced it with a file full of zeros and manually merged the end onto the original .part file with a tiny custom python script since I had already moved the incomplete file to other media before realizing I could try this. (In my case, the incomplete file would still have been useful even with the last ~1MB cut off.)

There are probably better options in most cases -- like Thunderbird for mailbox as other people suggested, or rclone for getting stuff from Drive -- but if you need to get Takeout to work and the download keeps failing this may be another option to try.