When i built mine my e shift valve also got stuck (frustrating after getting it all back together and having to take it back apart isn't it?
)
If i were you i would take the valve body back out and get some good cutting oil spray it in the valve bore and work it back and forth, making sure it slides freely (so it won't stick again). With mine the very last bit was the tightest, the very end (if you were to push it all the way in)of the valve would stick in the valve body and it took me a while to get it to freely slide.
Don't sand the valve, just have patience and work it back and forth.