It looks like only one stereo and one mono mix was ever done, so there was never any attempt to get rid of the error when it was released in later years.
This is from The Usenet Guide to Beatles Recordings ... (http://www.columbia.edu/~brennan/beatles/var-1964.html
basic recording- 1 Jun 1964
additional recording- 1,4 Jun 1964
master tape- 4 track
a] mono 4 Jun 1964.
UK: Parlophone GEP 8920 (EP) Long Tall Sally 1964, Parlophone PSLP 261 and PCM 1001 Rarities 1978-79.
US: Capitol 5255 single 1964, Capitol T 2018 Something New 1964.
CD: EMI EP box set 1991.
b] stereo 22 Jun 1964.
US: Capitol ST 2018 Something New 1964, Capitol SKBO-11537 Rock and Roll Music 1976.
UK: Parlophone PCSP 719 Rock and Roll Music 1976.
CD: EMI CDP 7 90043 2 Past Masters 1 1988.
Stereo b] has the vocal and piano much louder (or one might say the rest is softer), and a cry "ow" is heard only in b] just before the guitar at the end.
The vocal has a doubletracking error at what should be "now you got a boyfriend down the street" in verse 2. This is heard less distinctly in mono [a], as if the bad track were mixed down at that point, but it is there, marking it as the same vocal and not different as reported elsewhere. The bad vocal track seems to have "girlfriend" for "boyfriend"-- however, on the BBC radio version (11 months earlier than this EMI recording) John sings "now you don't care a dime for me", which is possibly what is here too.