Since the cypher ends in a single letter, try working it backwards.
Remove all double letters that appear ...either just use the letter once
or remove them completely.
ie...the fifth cypher is tyccq
remove the two c's
either replace it with just one
or take them out completely
reverse the order
this is just a guess. do that with every double letter in each occurrence.
reverse the cypher so it starts with e..
then use this...
simply enter the cipher and try to see if it can help you.
or try it with the idea you had with the mmbct where there is a space between
cypher4u is right all the letters are used and its five letters per "word"
try every fifth word.
i suspect there are null letters in there, im assuming its the double letter instances.
another way to look at it would be to find the most common letter used
count each letter ..find how many times each letter is used and look for a pattern.
the solve could be in the pattern not the letters themselves.
i dont know if this helps but its better than a grouchy response.