When I was in the seminary, one of the priests who was trained in Econe in the late 70s/80s told us about a modernist plot that was discovered in the seminary when he was there. Seminarians who had been sent as infiltrators by modernist bishops were meeting secretly in the vineyards at night after compline to discuss the various seminarians and how to corrupt them.
My good friend An. L. was a seminarian in Écône for about 3 years, I am thinking around 1986, and discovered a bunch of modernist / kommunis "seminarians" plotting evil agendas. He reported this to the authorities and as he felt there was a threat for his safety / life he immediately came back to Canada.
"Join the sspx" the saying goes,"and you will meet every type of people".
I don't think +Fellay is an infiltrator though, he just took the modernist bait. Fr. Franz Schm...was saying from the pulpit, Winona 1989? , that the first reason incense is used for ceremonies is to cover up body odor from all the ones in the sanctuary! "This is true" he added. Nithe spirituality.
Pray.