Seed phrase checksum

I have a program I’m working on in plain old C language that requires the user to flip a coin 128 times. This provides 128 bits running over SHA256. The first byte (leftmost character?) of that hash must be converted back to binary and added to the initial entropy. This gives 132 bits to form 12 seed words. But the last word is never right. There is something wrong with my logic. Can someone find it and tell me what I should do?? Here’s an example: Let’s say the user flipped their head 128 times. It will be 11111111111111111111111111111111111111111111111111111111111111111 111111111111111111111111111111111111111111111111111111111111111111. If you run this through the hash, I get 5ac6a5945f16500911219129984ba8b387a06f24fe383ce4e81a73294065461b. The first (leftmost) character is the hexadecimal number ‘5’, so we convert it back to binary to get 0101. So now it’s 132 bits. 111111111111111111111111111111111111111111111111111111111111111111 11111111111111111111111111111111111111111111111111111111111111110101. This should give me the following seed phrase: "zoo zoo zoo zoo zoo zoo zoo zoo zoo zoo zoo wrist" But that’s not right. Ian Coleman’s web page states that the correct answer is: "wrist" And the sparrow purse says "wrist" Not a valid checksum. Where did I turn on the road?