Menu in source code different than on view port

Hi,

I have a strange issue and I tried everything I can think of but nothing works.
Hopefully you can find it.

In the source of the webpage (see private area) there's a menu-item-16080 that's not specified in wordpress Appearance. It is also not displayed on the view port. If I take a further look, on the view port there are five menu items below Alimentatie (this correct) and in the source code only four (this is not correct).
What I want is five menu items in the source code, as they are shown on the view port.

I disabled caching, manually cleaned at server side the cache and restarted the PHP engine. But I still have a difference between source code and view port.

Can you find the problem? I hope I specified my problem clear enough.

Thanks Henk.