It isn't RTT that can't cope, this is the data supplied.
801222 working 1E10 1000 Edinburgh to London Kings Cross is running over an hour late into Kings Cross.
https://www.realtimetrains.co.uk/service/gb-nr:C86141/2021-08-01/detailed
801213 is due to be working 1S23 instead having arrived at Kings Cross on a previous service - 1E09. A fresh unit appears to have been sourced earlier for 1S22, the preceding service to Edinburgh.
Trains being diverted via Hertford North at the moment due to a person hit by a train between Stevenage and Welwyn Garden City.