Some additional Information:

In calendarfetcher.js and nodehelper.js is the following line:

const Log = require("../../../js/logger.js");

If you copy the “calendar” folder down to “modules” this reference will be broken.
So you have to change to:

const Log = require("../../js/logger.js");

Hey guys,

got a similar Probem with the Weatherforecast Module working with Pages Module.
Weatherforecast is configurated on just one Page and shows up on every Page after update.

I guess found a solutiion on that:
On Weatherforcast.js on line 377

this.show(this.config.animationSpeed, { lockString: this.identifier });

is called. I guess this has to be done, when Module is shown up to update UI, but not if Module is hidden.
So

if (!this.hidden)
    this.show(this.config.animationSpeed, { lockString: this.identifier });

does the trick.