It looks like all USPTO systems (TEAS, MyUSPTO, Patentcenter, EFS-Web, PAIR) are broken or very very sluggish. Listserv members are reporting timeouts, forced logouts, and lack of responsiveness from the USPTO systems.
As is so often the case during such crashes, there is no mention or acknowledgment of any of this on the USPTO system status page.
I have filed responses through internet outages (using a hotspot), power outages (at Starbucks) and equipment failure (using a back-up laptop). Turns out the IT system of a solo practitioner can be more reliable than the USPTO…
Just before 5:30 ESTI filed a new provisional application in PatentCenter with no problems or sluggishness. And then I had no problems filing to record an assignment in EPAS.