IE11 - Dropdowns don't open

[PaulKahl]

This is using Froala in an AngularJS 1.7.5 page, with Bootstrap 4.3.x.

Expected behavior.
Dropdown lists (font size, color, etc) should function correctly in all browsers the client works in.

Actual behavior.
In IE 11, the dropdown lists don't always open.

Steps to reproduce the problem.
I embedded the Froala control in my page per the instructions.

Editor version.
3.1

OS.
Windows 10, Windows Server 2012 R2

Browser.
IE 11

Recording/Screenshot.