I'm having problems with rear tyres coming close to rolling off the rim on my 27.5 Anthem.
I'm running Stans Arch EX rims, and used to run a snakeskin Racing Ralph 2.25, but due to this problem I've recently changed to an Ardent EXO TR 2.25 on the rear.
During high grip hard cornering off the brakes, the tyre rolls to the point where it is about to burp, but doesn't burp. All grip is lost for a second or so.
It happens most rides, tyre pressure is always between 30 to 35psi, running tubeless with stans sealant.

Any ideas?
More pressure?
Wider rim?

Cheers.