It's a lot of code but line 449 and 455 are the lines of code that has the logic
for writing a string, and line 547 to line 618 are the lines that are important
for dumping NBT, and line 681 onwards are just a simple test for the NBT data
(the parser works, s it's just the dumper that is broken)
My issue is that writing my string to an NBT file seems to corrupt the data
somehow...

too many lines of code yes, but ehe trimming it down would take ages :p
https://play.nim-lang.org/#pasty=DFZSPzFmJFav