I have modified Logback1759Test as suggested. See commit aa689782

Moreover, running the test with logback version 1.3 (JDK 11) or version 1.5.3 (JDK 21), Windows 11 under CMD or cygwin's xterm does not reproduce the issue. I have also tested with logback 1.5, JDK 21, Windows 10, with CMD.exe or cygwin's xterm, without success.