This is a known issue and we are working on a fix.
To give you some background, the issue is happening because by default Joomla & all 3rd party extensions use the default Boostrap 2 modal but since Astroid is based on Bootstrap 4. It's breaking things and conflicting with them a bit.
We hope to have a fix soon.
If you like our support and products, tweet us at joomdev and let the world know about it.
The issue is happening due to loading of 2 bootstrap js (3 and 4). We must disable either Joomla's bootstrap or Astroid's bootstrap. So we added an option to disable Astroid's Bootstrap 4. You can have a copy of our dev branch and test it. After installation you must disable Bootstrap from Plugins >> Astroid Plugin >> Options
JoomDev is not affiliated with or endorsed by Open Source Matters or the Joomla! Project. The Joomla! logo is used under a limited license granted by Open Source Matters the trademark holder in the United States and other countries.