Holy broken geometry...
I am not sure what is corrupted exactly, but if you drag the "End Of Part" marker up to "Boundary Patch 2", there will be no issue. Moving the EOP marker above that crashes Inventor. That Boundary Patch is what I guess is corrupted if I had to bet, and you will see below why...

I removed all file links (simulation and other embedded links, seen at Tools tab > Links), then I deleted all features except for the faulty Boundary Patch 2 and its suspicious 3D Sketch1. I unshared Sketch 1 and deleted Boundary Patch 2, then saved the file with a different name. Now, I was able to edit the 3D Sketch and use, instead of simple "Delete", the TRIM function. I had to click 16 times to delete this section in your sketch to finally have it cut off!
Either all those links or geometry sharing the same sketch based on overlapping lines breaks Inventor, or maybe just the fact that the whole thing is using some pretty weird (bad) practices to create something so simple.
Anyways, attached is the fixed 3D Sketch and I hope you can reconstruct the rest back from this point on. Trying the same operations (trim) on the original file will not work and also crashes Inventor.
