Lay your machine on it's side. If water comes out it has collected on the base plate and triggered a detector. Take a look at your door seal. If it is dirty and encrusted give it a good clean, especially where it meets the base (use a cotton bud to get right into the corner here). A local repair man who checked my machine suggested that this dirt was allowing a small leakage which collected in the base, thus the F7 signal. I gave the seal a really good cleaning. That was about 6 washes ago, and - touch wood- it's been fine since.
Roy Butterfield, September 2010