Most likely a general Proton + XIGNCODE3 issue.
So nothing to do with the CrowFPS\\Binaries\\Win64\\CrowFPSClient-Win64-Shipping.exe calls via double backslashes?
There's no reason to expect that to be a problem. It looks like an argument to the game exe which would access the file using the Windows API and thus backslashes would be translated.
Yes, the initial problem with unable to connect to server is somewhat related to extra quotes for the process spawned by the game through ShellExecuteW, due to the extra quotes (how that is supposed to work is a separate story) it cannot correctly parse command line and specifically server address.
That is solvable one or another way but then it wants Xigncode3 kernel mode driver. User mode Xigncode works for some games in Proton now, but xigncode with kernel driver looks pretty much as a blocker for now.
Nothing extracted yet.
Compatibility Report
System Information
I confirm:
Symptoms
Game does not start. Seems to me there are hardcoded backslash file paths.
steam-1692070.zip
Reproduction