Well, slightly embarrassing :oops:
Of course I hooked up the spunding valve to the liquid out post... yeah!
The tradition of sampling the previous brew was maybe to blame here ?!
Using a FermZilla All Rounder with a BlowTie Spunding valve I'm 24+ hours into fermentation and the pressure was at 30 PSI.
I opened the spunding valve to dial down the pressure and the wort started pouring out of the spunding valve!
I had to release pressure using the PRV and it seems I can't...