The regular input() used in a thread function is producing additional newline.
The solution is simply do not use the input() inside the threaded applications.
Instead you should use sys.stdin.readline().strip().
The input() produces additional line because it thinks that it needs to produce it.
And also the stdin stream automatically attaches a newline,
therefore using .strip() makes sure it won't happen.
Sources:
https://stackoverflow.com/questions/31142566/print-skipping-newline