Question for the Stan's Experts

I have been using Stan's Arches on my 29ers for the past six months and have successfully mounted up the following tires:

2.25 Schwalbe Racing Ralph
2.1 Bontrager Xdx Tubeless Ready
2.1 Kenda Small Block 8
2.1 Schwalbe Little Alberts
2.35 Panaracer Rampage

I follow the instructions on Stan's video carefully and use an air compressor to inflate. I do not add Stan's sealant until I can get the tire to seal with just soap on the bead.

Why can't I get the Little Alberts to seal again??? They were the trickiest of the tires listed above the first time I mounted them but with lots of soap on the bead and some patience I got them inflated and they held air well. I tried everything this weekend and cannot get them seated.

I wonder if the SnakeSkin sidewall is preventing the bead from making the initial seal? Sure, I could throw a tube in their but what fun would that be?

Any tricks out there?