Emulator

Game Name?
Super Smash Bros. Brawl

Game ID?
RSBE01

What's the problem? Describe what went wrong in few words.
Possible desync error message pop up upon launching Project M.

What did you expect to happen instead?
No desync.

What steps will reproduce the problem?

1. Configure GameCube Controller then make the controller device inactive, but don't change in the device dropdown. That happened on my secondary PC which was joiner of the game I'm hosting on my primary PC.
2. Have virtual SD card packed with Project M - Hackless method (see how: https://wiki.dolphin-emu.org/index.php?title=Virtual_SD_Card_Guide).
3. Start Brawl then launch Project M through Stage Builder in the Brawl menu.
4. Check Netplay chatbox for desyncs.

Dolphin 3.5 and 3.5-367 are old versions of Dolphin that have
known issues and bugs, so don't report issues about them and test the
latest Dolphin version first.
Which versions of Dolphin did you test on?
4.0-7322

Does using an older version of Dolphin solve your issue? If yes, which
versions of Dolphin used to work?
I'm assuming none.

What are your PC specifications? (including, but not limited to: Operating
System, CPU and GPU)
Host PC: Official GameCube Controller Adapter for Wii U
Joiner PC: PlayStation 3 Controller (Scarlet.Crush's Xinput Wrapper for DS3)

Both of my PC are high end with overclocked Intel CPU's. They can run Dolphin super fine.

If you couldn't reproduce this then I will throw more details sometime later.