Progress bar rapidly jumping to 100% then times out

I've been having an FTP problem for a few weeks where the upload progress bar jumps to 100% rapidly. It's only doing this with upload. It seems like it's trying to fire out the upload at insane speeds that the receiving device can't handle, then crashes. This is an issue on, Windows Explorer, FileZilla, CyberDuck and WinSCP.

On FileZilla the way I got around this was adding a speed limit but it was only a band aid solution. It feels like I've exhausted every little obscure FTP setting in Windows, nothing is fixing it.

This isn't specific to a particular server either. My phone, Xbox, PS2, Wii, Wii U, 3DS all do the same thing.

I've ruled out my ISP messing with the FTP as I've tried connecting my Xbox to my laptops Ethernet port directly with a patch cable and the issue still persisted. Wifi and Ethernet over network act the same way too.

FTP works fine on my old 2010s era Desktop so that narrows it down to my Laptop/Windows install being the problem. I'm totally lost.

https://drive.google.com/file/d/1UIAt3C_oDFX0y4EdkduGSgLWJng991aS/view?usp=sharing
Here is a video showing the problem. As you can see after the timeout the file is still being uploaded in the background.

System specs/important info[u]
WinSCP V6.3.4
Windows 10 Home 64 bit 22H2 19045.4780
Asus Tuf F17
Core i5, 32gb ram 1650ti

Sorry, no idea. Does the problem occur with other protocols?

As a workaround, you can throttle the speed in WinSCP too.
https://winscp.net/eng/docs/ui_transfer_custom

You can also try to disable "Optimize connection buffer size":
https://winscp.net/eng/docs/ui_login_connection

From what little I can gather from other forums it's something to do with the buffer/socket size being out of whack.

I did preform a Windows 10 debloat script in July and that's roughly when the issues began. Maybe it ruined a registry entry or something?

There's a Windows guide talking about adding "DefaultSendWindow" into the AFD folder in Regedit but that hasn't seemed to make a difference.

Great news, it's fixed :D
In the end after all that... it was just Bitdefender messing with stuff.

I had turned off all the firewall stuff LOTS of times during testing to see if it was the firewall but it still had issues. Completely uninstalling all Bitdefender software did the trick.

Of course I can't be without an antivirus so I'll reinstall and find a way around the buffer issue.

Otherwise, case solved :>

Thanks for sharing your findings!