Error Cannot assign property 'watch' in JS when embedding on odoo website

[Daidalos]

I have tried many different ways to implement the 3cx live chat code into an odoo 8.0 website, but with no result.
The following error is raised:

Uncaught TypeError: Cannot assign to read only property 'watch' of object '#<Object>'
at cdn.3cx.com/livechat/v1/callus.js:23:69863
at cdn.3cx.com/livechat/v1/callus.js:23:66317
at cdn.3cx.com/livechat/v1/callus.js:23:67712
at Array.forEach (<anonymous>)
at lr (cdn.3cx.com/livechat/v1/callus.js:23:67684)
at cdn.3cx.com/livechat/v1/callus.js:23:68381
at Nh (cdn.3cx.com/livechat/v1/callus.js:27:181501)
at Module.293 (cdn.3cx.com/livechat/v1/callus.js:27:184030)
at __webpack_require__ (cdn.3cx.com/livechat/v1/callus.js:27:393538)
at cdn.3cx.com/livechat/v1/callus.js:27:394602

Maybe it depends on slow DOM build of old odoo js framework. But I haven't found any solution to make callus.js wait for finished dom.
Any Ideas?