I’ve had a look, and actually 5R90 (which is part of the morning diagram that consists of 5R90 Feltham Depot to Hounslow, 2R90 Hounslow to London Waterloo via Brentford, 2S09 06:22 London Waterloo to Weybridge via Hounslow, 2S18 08:02 Weybridge to London Waterloo via Hounslow and 5Y84 09:37 London Waterloo to Wimbledon Park Depot) was a 701 from 27th February to the 3rd March, and then again last Saturday 7th March. It was a 8-car 458/4 last Wednesday, Thursday, and Friday (4th, 5th and 6th March). It is booked to be a 458/4, but it was being covered by a 701 because of the ongoing reliability and availability issues with the 458s, which as you mention is continuing today as well. 2S18 in particular is a very, very busy service from Hounslow onwards (in my experience working those services) so hopefully that diagram is earmarked to become a 701 permanently sooner rather than later. With an 8-car 458/4 many people are unable to board and are being left behind from Barnes or Putney onwards.