I am using a HC-SR501.
As you are operating your mm in portrait mode, maybe it is an performance issue.
Here is a link you can try https://forum.magicmirror.builders/topic/9707/save-performance-when-rotating-screen-e-g-on-raspberry-pi
Maybe this helps.
Are you sure your link example is complete?
Is the following example
$ curl -X GET http://magicmirrorip:8080/api/module/alert/showalert?message=Hello&timer=2000 working?
Details see https://github.com/Jopyth/MMM-Remote-Control/blob/master/API/README.md
Hi to all MagicMirror users,
i just released Version 2 of my MMM-Dreambox module.
git pull in the MMM-Dreambox directory.
Thanks to @evroom for testing on different enigma2 receivers.
Maybe not a direct answer to your question, but you can also use calendar .ics files for displaying holidays (with the default calendar module of mm), see links: