There was a thread a couple weeks back. The FSSP was conducting a local pilgrimage terminating at the Basilica. They had written for permission to say the Mass far in advance and had received it. But at the last minute, the day before the pilgrimage, someone in the chancery put 2 and 2 together and figured out that the FSSP would be saying a (gasp) Latin Mass and this would set a terrible (according to them) precedent. So they withdrew the permission at the last minute saying that they would need to apply for a special indult and it would take weeks, etc.
What are some bishops so afraid of? There is no exlaination good enough to excuse forbidding a one time Tridentine Mass - especially said by a growing order. And you know what? Because the FFSP isn't progressive, they obeyed the bishop even though the directive is inexplicable. Wonder if McCarrick even knew about it.