Normally, at weekends, depots such as Exeter, expect to have a number of dmus undergoing routine maintenance but when units experience serious sliding the consequent wheel flats require the wheels to be changed at the first opportunity. Normally the depots are able to release spare units at weekends to strengthen trains in order to cope with surges in demand such as sporting events or Christmas shopping but clearly this cannot happen when so much extra work needs to be undertaken. On weekday mornings, every available vehicle is needed to cope with commuter traffic and the depots must give priority to getting units back in service for Monday morning.
Very many thanks to Derek for that very comprehensive report - now we understand the problems which FGW have to cope with and are doing their very best to overcome. Well done FGW.