Hi, and welcome:
This happened to me recently when I changed the data structure of a form and then closed it when there were still errors in one view.
You've removed the references to ChangeSection1_5 -- so what are your new errors? For me, I had several controls that I ended up removing from manifest.xsf before I was able to reopen my form in design mode. So I'd remove refs to the first control, then I'd get errors relating to another control. When I finally had all the controls removed, I was able to open the form again...