The worst bug I've ever encountered was a JS file that kept not running, with very cryptic and hard to understand trace that made no sense. TypeScript and others parsed it fine without any issues.
After 3 days of literally trying everything, I don't know why, I thought of rewriting the file character by character by hand and it worked. What was happening?
Eventually opened the two files side by side in a hex editor and here it is: several exotic unicode characters for "empty" space.
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