Problems W/ Adaptive Huffman Code

Hi! I am working on my own version of the Adaptive Huffman Code technique. It is based on Vitter's technique. Now, one test file gets corrupted starting at the fifth byte. I added some debugging code to the compressor, and, on the fourth byte, a 1 bit is written instead of a 0 bit. It is a NYT and should only get 0 bits. I attached two code snippets which could be causing the error. Does anybody have any advice?