I played a bunch of Yom Ha'atzmaut gigs last week. Several of these were for schools. I've discovered that at many schools they are singing the melody to Im Eshkacheich (the R' Mottel Twersky version) wrong. Specifically, these groups have adapted the first few bars of the B section so that they sound like the B section of Etz Chaim (the Tanchum Portnoy version).
They sing the words "Im Lo Aa'leh Es Yerushalayim" to the melody used for "D'racheha Darchei Noam".
I suspect it's because of a background choral part they've heard/learned. Ironic, since the melody of Etz Chaim as it is popularly sung in shuls has also evolved from the original. I suspect that a harmony part was the cause in that case too.