»Pile-up at Church and Duboce

Where is the Church on Church St.? And what happened to the N-Judah this morning? Just before 0800, a 2-car N stopped outside the Market Street Subway entrance and sat there for several minutes. The next warning came from the destination sign: it started rolling towards "J" and then "F" and finally came to rest nowhere in particular.
Two 2-car trains stacked up between the Duboce Park station and the intersection(*) of Sanchez/Steiner and Duboce; another two Ns were stopped between there and Church. Automotive traffic was not pleased: another reason for a transit-first policy on this stretch.