I agree with you, but I'm stuck there too.
Hey, I uploaded a version with post-jam fixes (adding an outline to the letter puzzle) so it should be a bit easier.
Also find a solution below:
Still having trouble. I had all the other pieces locked in so I knew I had it right overall. I just couldn't find the exact pixel this last piece was supposed to go.
From my experience, I couldn't complete the puzzles when using the video settings x2 x4 etc... The only one that worked is fullscreen "stretch, respect aspect ratio", I think the upscaling kinda mess up the hitboxes.
So sorry it didn't work again :/ Thanks for your patience and for keeping to try it. I'm trying my best to fix it and have increased the detection area for the pieces, but there's still a chance the issues will occur. :(
I was able to complete it! According to the LD rules you're allowed to update your original build with bug fixes, so I don't think it would be unreasonable to backport this fix to your non-post-jam build.