ASP.NET Core Bootstrap 4 Accordion only partially expanding

I’m trying to generate an accordion dynamically using bootstrap and ASP.NET Core.
The goal is to show all terms which belong to a certain category but the problem is that only the first two out of four categories are expanding/collapsing. I can see, that each card-header and card-body is available in the DOM.
My code looks like this:

Bootstrap 4.5 Dropdown appearing as multiple links on iOS

When I try to load a dropdown list in a Bootstrap navbar on an ASP.NET page, the desktop version of the list loads exactly as it appears on the official navbar documentation, but not when loading the same page on an iPad Air 2 with iOS 13.3.1. Instead of loading the listed items in a dropdown fashion, they appear below the dropdown menu’s name. Just as well, the toggle “hamburger” button appears as a blank button.
Bootstrap 4.5 Dropdown appearing as multiple links on iOS