Accordion in modal will not collapse

I want to have a modal with two accordions each with a form.

I can’t figure out why this accordion will not collapse.

https://snippet.webix.com/ntp2hllh

Here is a simple example of a working accordion.
https://snippet.webix.com/f50td923

I guess you can’t have a view: form inside an accordion?

Okay for some reason the problem is multi: false.

https://snippet.webix.com/qn9pdh5b