Super easy. They're Schwalbe Kojaks on a Velocity A23 (tubeless ready, I'm assured). Not specifically tubeless ready tyres (this is an experiment), but they seem to hold the pressure up to about 90psi before all the air escapes out the valve hole.
It shouldn't be this easy, but then you did have a non-tubeless ready tyres, my experience is only on tubeless tyres and it should always have a tight to near impossible fit (pray it's not the latter).
Sound like you answer your own question TBH; replace valve.
Quick question - how easy is it to mount the tyres?