Dunno if it's helpful for diagnosis, but my 01.txt that yields the expected sha256 sum ...
... is 0x3E1051 bytes long
... starts with <<Congratulations>>, as you already knew it should
... ends with <<IX%7M3+]vW7+zB]{\>>
(It couldn't be line-ending issues, could it? Do you have any 0x0D bytes?)
And, just in case it helps, my original text file (before stripping everything up to 1.#####, and _without_ the spurious 0x0A byte) is 0x3E404D bytes long and ends with << vhuY!niauago>>.
... is 0x3E1051 bytes long
... starts with <<Congratulations>>, as you already knew it should
... ends with <<IX%7M3+]vW7+zB]{\>>
(It couldn't be line-ending issues, could it? Do you have any 0x0D bytes?)
And, just in case it helps, my original text file (before stripping everything up to 1.#####, and _without_ the spurious 0x0A byte) is 0x3E404D bytes long and ends with << vhuY!niauago>>.