The tyres are hooking into the bead when inflated, but the air leaks out around the valve stem (no sealant), then looking at the tyres just now the bead has come out again.
Leaking around the valve stem usually means your tubeless tape isn't sealing the spoke holes. Maybe your tape is too narrow, or just not sticking good enough..
@mdcc_tester Are those UST tyres any good? What tyres are you using?
The tyres are hooking into the bead when inflated, but the air leaks out around the valve stem (no sealant), then looking at the tyres just now the bead has come out again.
Does this mean it was never in properly?