So to fix the issue, find where beam-mp is installed to. For me it is "C:\Users\YOURUSERNAMEHERE\AppData\Roaming\BeamMP Launcher\" Within this folder is a folder called "Resources." You'll want to download the map off of this forum from somewhere here and place it in that resources folder...

I'd like to chime in with a similar issue. Buddy of mine can play all 2fast servers except the Nordschleife server. Consistantly makes it to 81% download of the map and he gets a code 1 error disconnect from the launcher message. Sounds like these might be the same issues.