latest self build commits crash on start

Is it just me? My self build lasts commits crash on start, the corresponding nightly builds do though?
I can build and run 9a05406 (and my changes on top), but not 9d32a42 (and any of my changes on top), 7 commits later, just crashes, very early, after the splash screen, and shows the following in the output window:

Starte C:\Users\joschmitz\Documents\GitHub\MuseScore\win32install\bin\mscore.exe...
InitTime : multimedia timer resolution set to 1 milliseconds
Cannot connect to named pipe after wait = \\.\pipe\server_jack_default_0 err = 2
Cannot connect to server request channel
Execution of JACK server (command = "C:/Program Files/Jack/jackd.exe") failed: No such file or directory
Cannot connect to named pipe after wait = \\.\pipe\server_jack_default_0 err = 2
Cannot connect to server request channel
Cannot connect to named pipe after wait = \\.\pipe\server_jack_default_0 err = 2
Cannot connect to server request channel
Cannot connect to named pipe after wait = \\.\pipe\server_jack_default_0 err = 2
Cannot connect to server request channel
Cannot connect to named pipe after wait = \\.\pipe\server_jack_default_0 err = 2
Cannot connect to server request channel
Cannot connect to named pipe after wait = \\.\pipe\server_jack_default_0 err = 2
Cannot connect to server request channel
jack server is not running or cannot be started

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
Open error: is JACK server running?
C:\Users\joschmitz\Documents\GitHub\MuseScore\win32install\bin\mscore.exe beendet, Rückgabewert 3