did try a few of my suppliers all i got was obsolete
these are a common problem to stick open i think the problem may occur if the unit is not rinsed out with clean water when finished
you could try lubricating it with a silicon based lubricant and see what happens
just done same job on my dads but i had one lying around last one i had i am afraid
typed vax valve in google
this one for a v026 think it may fit but some had tools water add on some did not
they are not saying its obsolete may be worth an email