I have created a new issue
  https://github.com/rordenlab/MRIcroGL/issues/35
Unfortunately, I can not replicate this issue on my system. Can you try these two methods in sequence to see if they resolve your issue:

1. Install the v1.2.20211007 .dmg 
 
https://github.com/rordenlab/MRIcroGL/re...

2. If this fails, does launching the application from the terminal command line with the "-r" argument resolve the issue? This varies depending on your installation location, but for most users it is:

/Applications/MRIcroGL.app/Contents/MacOS/MRIcroGL -r