Did you cut each piece the same length size......or just use one long piece a merrily sew along.....
I have found from past expierence that does work for me as I must cut each piece the exact size....
did you square your blocks...before adding the sashing....if you cut it the exact size, did you half then
and then quarter mark and then pin.....I am just trying to pull anything I can from my feble brain.....