North of the phase break there is a voltage fluctuation issue. The ACSs do not like this and will open the MCB if there is too much fluctuation in too short a time frame.
There is no space in Suburban to stub trains, 0 and 5 have spare equipment, 6 and 7 have Vs that are waiting for repairs. There is also no real tangible need or want for a train which does not go through the tunnel.
The most recent news indicates "at or around the week after Labor Day" for the problem to be fixed. I'm guessing that means the equipment will be back then, but to be fair the only people who seem to be up in arms about it are buffs.
"It's not even a railroad anymore, it's a circus act."