As far as the Circle, District, Hammersmith & City, Jubilee and Metropolitan lines are concerned there are indeed more "faulty trains" than is the norm (although it's important to note that not everything publicly billed as a faulty train is, in fact, a "faulty train", in the same way that "minor delays" can easily be thirty+ minute gaps in some places).
For the rest of the network, it's generally no more or less than is the norm for this time of year - leaf fall has an impact on some lines, whilst other lines are impacted by with ageing fleets, reduced investment and increased running.