Why text disappears when saving scss file?

Question

Sass

var gulp         = require('gulp'),
    sass         = require('gulp-sass'),
    autoprefixer = require('gulp-autoprefixer'),
    csso         = require('gulp-csso'),
    rename       = require('gulp-rename'),
    browserSync  = require('browser-sync').create(),
    concat       = require('gulp-concat'),
    uglify       = require('gulp-uglify'),
    pug          = require('gulp-pug'),
    notify       = require('gulp-notify'),
    del          = require('del'),
    uncss        = require('gulp-uncss');

gulp.task('browser-sync', ['styles', 'pug', 'scripts'], function() {
    browserSync.init({
        server: {
            baseDir: "./app"
        },
        notify: false
    });
});

gulp.task('pug', function() {
  	return gulp.src('app/pug/*.pug')
    .pipe(pug({
      pretty: true
    })
    	.on( 'error', notify.onError(
      {
        message: "<%= error.message %>",
        title  : "PUG Error!"
      } ) )
    )
    .pipe(gulp.dest('app/'));
});

gulp.task('styles', function () {
  return gulp.src('app/sass/**/*.scss')
  .pipe(sass({
    includePaths: require('node-bourbon').includePaths
  }).on('error', sass.logError))
  .pipe(rename({suffix: '.min', prefix : ''}))
  .pipe(autoprefixer({browsers: ['last 15 versions'], cascade: false}))
  .pipe(csso({
    comments: false
  })) //minificator
  .pipe(gulp.dest('app/css'))
  .pipe(browserSync.stream());
});

gulp.task('scripts', function() {
  return gulp.src([
    './app/libs/modernizr/modernizr.js',
    './app/libs/jquery/jquery-1.11.2.min.js',
    './app/libs/waypoints/waypoints.min.js',
    './app/libs/animate/animate-css.js',
    ])
    .pipe(concat('libs.js'))
    // .pipe(uglify()) //Minify libs.js
    .pipe(gulp.dest('./app/js/'));
});


gulp.task('watch', function () {
  gulp.watch('app/sass/**/*.scss', ['styles']);
  gulp.watch('app/libs/**/*.js', ['scripts']);
  gulp.watch('app/js/**/*.js').on("change", browserSync.reload);
  gulp.watch('app/**/*.html').on('change', browserSync.reload);
  gulp.watch('app/pug/**/*.pug', ['pug'], browserSync.reload);
});

gulp.task('default', ['browser-sync', 'watch']);

That is, when you save the *.scss file, the text on the screen disappears, although if you look at the page code, then everything is fine.
But if you refresh the page, then everything returns, then when you save * .scss again.

Answer 1

I removed caching from the browser, it helped me.