BNSF's Southern Transcon is being badly affected by crew shortages and saturation to the extent that certain types of freight are being embargoed (not accepted for shipment) to/from California. They are having trouble moving their own trains, let alone Amtrak.

Not to say at least some of it isn't self-inflicted. They were already short crews and BNSF's new Hi Viz attendance and availability policy caused a wave of resignations.

The bottom line is BNSF is having trouble moving trains right now and Amtrak is caught in it.