Word on the grape vine is that there's been enough comments about 'vibrations' on one train in particular for them to be taking precautions. The 'vibration' is worse the further back you go.
I personally can't help people are being over sensitive though. Aside from the last corner where the train oddly shuffles, the rest of the ride is graceful, intense and smooth. It seems a bit over the top to me but maybe Towers are just being cautious and doing any work they can now before the Easter holidays.