Dear Mars,
I am not an expert in using telnet, but I am wondering if this duplication of the command could be related to the mode telnet is using. Is echoing of the local characters enabled? If so, you might try to switch it off. According to [1] this should be achieved by using "^E" ...
Cheers,
Ralf.
[1] telnet(1): user interface to TELNET protocol - Linux man page