Error when starting gallp. Gulp SyntaxError in plugin "gulp-uglify-es"?

Question

gulp.js

Good to everyone.

When running gulp with the gulp command, the plugin gives the following message:

SyntaxError in plugin "gulp-uglify-es"
Message:
'return' outside of function
Details:
filename: app.js
line: 1851
col: 1
pos: 59594

on the plugin's off page ( https://www.npmjs.com/package/gulp-uglify-es ) there is this message:

gulp stream to uglify with 'terser' (es6 supported).

terser is the new 'uglify-es'. uglify-es is no longer maintained.

Is the error caused because of this or am I looking in the wrong place at all?