I'm not quite clear on what's going on.
Are they being fully seated (showing the witness line all of the way around)?
Are the tires coming unseated at low/no pressure? Otherwise, I'm not understanding why you had to re-mount them, unless you're not adding sealant through the stem (which is, IMO, the easiest and cleanest way to go about it).
What tires are you using? You're aware that they need to be ETRTO TSS spec tires (for hookless/straight sidewalls)?
For the initial install, if the tires are fully seated, and you've got sealant in 'em, I'd at least let 'em spin for a good few minutes, if not go for a short ride. Some tires carcasses are more porous than others, and need to have that sealant really seep in.