I work with @Leonel_Bonnici and we were trying to diagnose the error together.
@Mihai_Dunareanu we opened a new project, updated all packages and used the read range activity, which worked normally. We also closed and re-opened studio and the activity loaded normally again.
What we also tried was for leonel to upload his latest version to our GitHub page so that I could download it and open it, and the same issue happened when I opened the process on my machine. We actually have an older version of the process, and the issue is not happening on that version, so as a work around we will revert to that version and continue working on it, but we would really like to know why we are getting this issue.