Firmware flashes fine but output freezes at "Closing Port..."

[SirTimmyTimbit]

I followed all the instructions. Whenever I try to flash a firmware on the Alt it flashes and the keyboard boots back up just fine, but the output freezes at Closing port... without SUCCESS at the end.

Scanning for device for 60 seconds
...................
Device port: COM6 (SAMD51J18A)

Opening port 'COM6'... Success!
Found MCU: SAMD51J18A
Bootloader version: v2.20 Mar 27 2019 10:04:48 [alt]
Applet file: applet-flash-samd51j18a.bin
Applet Version: 1
Writing firmware... Complete!
Booting device... Success!
Closing port...

The terminal window freezes and I cannot use it anymore. I have to force close it and start a new one. I tried git-bash, cmd, powershell. I tried different terminals. Every shell and terminal freezes at that line.

I compiled the firmware at Drop's official configurator. I've also compiled qmk from scratch. Just the default firmware, no changes to anything. Same result.

I was using the YMD96 keyboard before the Alt, which had QMK as well. I had no problem compiling and flashing that keyboard.

This makes the process of making changes to the code and flashing very tedious. I'm also concerned if there's something wrong with the keyboard or the build environment I'm using.

I'm using

• MDLoader 1.0.3
• Up to date qmk_firmware upstream repo
• Windows 10 10.0.18362 Build 18362
• Anker A8173 6 feet USB 2.0 to USB 3 cable.
• I bought the Alt from someone else. He claims it's just a couple of months old with light use, and he mentioned he never experienced this problem with the keyboard.