SyntaxError with jquery-3.1.1

Due to security reasons I had upgraded jquery to version 3.x

No Problems with all my plugins – even the main functions of wpdiscuz are working.

But browser console is logging an error after submitting a comment with wpdiscuz:

SyntaxError: Unexpected end of JSON input
/wp-content/plugins/wpdiscuz/assets/js/wpdiscuz.js in line 372
function notifySubscribers:
    at parse (<anonymous>)
    at Function.a.parseJSON (jquery-migrate-3.0.0.min.js)
    at Object.<anonymous> (wpdiscuz.js)
    at i (jquery-3.1.1.min.js)
    at Object.fireWith [as resolveWith] (jquery-3.1.1.min.js)
    at A (jquery-3.1.1.min.js)
    at XMLHttpRequest.<anonymous> (jquery-3.1.1.min.js)

wordpress 5.1
wpdiscuz 5.3.1
– with WP native ajax functions
– comment of non registered users
– notify of subscribers is disabled