Holy spitballs! I FIXED IT!!
And I _somewhat_ know the ballfield of what causes it.
Okay, so each of the items involved I either accidentally created and just closed out the PNG editor with default, or I was making a new animation for that I changed my mind and left the blank animation in.
The Construct 2 image editor by default left "corrupt", unreadable pngs or pngs that had a reference an it just never saved them. So the next time the project was loaded it just flipped it's lid.
Removing all "empty" sprite references cleared it up. It's working now.
Wow. What a mess. Glad there was a way around it though.
I can easily show the unworking project and the functional one now, if needed, as I have copies of both. lol
EDIT: There is a post awaiting moderator approval (likely because of images) that explains my necro. Summary is that this exact same issue cropped up again 5 months later and broke my project upon closing out construct and trying to load the project again.