What has caused my Mercedes-Benz A180 to develop three faulty brake light switches?

Two days after buying a new Mercedes-Benz A180 in 2010, messages came up on the dash saying "ESP & runflat indicator not operative". The Mercedes garage said the brake light switch was faulty and replaced it. Some time later the same messages intermittently appeared but disappeared when the engine was turned off, and did not reappear when it was switched on. About six weeks ago I contacted the garage, who fitted another brake light switch and again told me the brake light switch was faulty. This weekend the same messages appeared yet again. It would be highly unlikely, although possible, that all three brake light switches were faulty. Do you think that there is an underlying fault in the electrical system or the on board computer?

Asked on 20 July 2013 by AO, Orpington

Answered by Honest John
Brake light switches are often the bearers of false messages on German cars and on some can lead to power being cut just when you need it. But in this case I wonder if the connection between the brake light switch and the ECU is interfering with the can bus electrics.
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