[sf.curbed.com]

"But when SFMTA Director Ed Reiskin asked whether this meant the weld holes were ultimately to blame for the cracking, Vecchio demurred, noting that while the holes were 'a significant factor',” LPI’s testing 'haven’t concluded what the driving force was.'

For example, Vecchio pointed out that they still need to determine 'where did all of those stresses come from?' and whether some flaw elsewhere might hypothetically have put undue pressure on the microcracks and caused the 'popping.' "