Source maps scss fell off. What to do?

Question

Sass

It often happens that on a new project, as the layout progresses, the source maps for scss suddenly fall off. Compiled via gulp

gulp.task('build-sass', function() {    
    return gulp.src('src/css/*.scss').pipe(sourcemaps.init()).pipe(sass({
        errLogToConsole: false,
        onError: function(err) {
            return notify().write(err);
        }
    })).pipe(minifyCss({
        compatibility: 'ie8'
    }))
    .pipe(sourcemaps.write('.'))
    .pipe(gulp.dest('dist/css'));
});

I couldn't find the reason for that. At first everything works, after a few days it may fall off (apparently due to something in scss). Restarting the browser or gulp doesn't help. Suddenly who faced it.
UPD: Moreover, the map files are created, but the usual css is shown in the console. Everything happens suddenly, on the 2nd or 3rd day of layout.