Repeated blowouts on rear of tandem

Hi All,

This is a weird issue I am having - hope one of you has an idea.

Rear Tandem wheel, 40 spoke Araya VX300 on a Santana tandem

Tires are Panaracer Pro Tite 700x32 new - I am using them on another Tandem bike just fine, no issues

I usually run them at about 120 PSI on the tandem (I...