This does appear to be what has happened. Traksy is currently showing 1B26 sitting in the platform at Carstairs, 1Z11 in the loop and 0S26 approaching Motherwell. RealTimeTrains shows 1S26 as running from Euston to Carstairs and terminating there due to a train fault and an additional VSTP 1Z11 from Watford to Motherwell. Looks like 1Z11 is being held to time, so an 0745 kick-out time at Motherwell. The thing I’m most surprised at in all this is that despite their staffing issues, they’ve found the additional guards needed to make 1Z11 happen.