I have this question too. I went to Gloucester Road and took the Circle to Notting Hill Gate. Couldn't see any work taking place in the small bits of District line-only track after emerging from the tunnel just before HSK (not suggesting that engineering work was not taking place). However, the District was fine on the way back to Southfields from Notting Hill Gate.
Report of a weld crack on points (trailing end of westbound District towards ECourt) 10mph implemented and track inspection done 12.05. Further inspection at 20.55 requiring suspension for this. Resumed 21.15.