Borderlands 3's launch has seen many technical difficulties, ranging from performance issues over DX12 troubles to silly upload speeds. Now the players are losing their progress due to cloud save corruption but there are partial fixes.
Borderlands 3 has seen problems with four major areas since its launch - frame rate trouble, DirectX 12 crashing, background upload speed and corrupt cloud saves that cause players to lose progress. Sadly, there is currently no community-made fix for the FPS problem and we will have to wait until Gearbox release a patch fixing the performance.
Meanwhile, the three other issues have some community fixes with mixed success behind them.
DirectX 12 crashing
In case your game is crashing on launch or just hangs forever, the issue may be caused by DirectX 12. In order to disable it, you will need to go to Documents -> My Games -> Borderlands 3 -> Saved -> Config -> WindowsNoEditor. You will find an .ini file in that last folder, named GameUserSettings that you can open with Notepad.
Find the line saying PreferredGraphicsAPI=DX12 and change the last number to "1" so it looks like PreferredGraphicsAPI=DX11. Save the file, close it and try launching Borderlands 3. This should cause your game to run in DX11 and avoid crashes.
Abnormal background upload speed
A long time Borderlands stream found out the hard way that he can't stream Borderlands 3 after discovering the game used all of his upload speed in the background. He also later found a way around this by using Netlimiter to block Borderlands3.exe which caused it to run in offline mode but also cut all the online features as well as the bonuses from the Super Deluxe Edition.
This workaround is by no means optimal but it should help at least those players with limited bandwidth or those with slow upload speed.
Cloud save corruption and losing save files
This one is particularly bad. Even the early build that was given to select reviewers had troubles with DX12 and saves disappearing, losing players hours of progress. It's hard to believe Gearbox were unaware of these issues but here they are, not fixed even in the launch build.
Anyway, not using cloud save option that Epic Games Store offers has reportedly worked for some people but not everyone. Local saves also seem to get corrupted.
Thankfully, some players managed to find a way around this. Similarly to the DX12 fix, you will need to navigate to Documents -> My Games -> Borderlands 3 -> Saved. This time around go for the Saved folder and find a file named 1sav~gibberish.tmp, rename it to "1.sav" and overwrite the existing file when prompted.
You should have both 1.sav and 1sav~gibberish.tmp in the folder at all times so make sure you copy the uncorrupted "gibberish" file before overwriting 1.sav with it. In case there is no 1.sav file in the folder, then copy the gibberish one and rename the copy to 1.sav.
Borderlands 3 players were invading Borderlands 2 forums on Steam at the time of writing but we would suggest you refrain from doing so - Borderlands 2 still has many players and those people would like to keep their forums on-topic.