Since the last software update (I think) my 705 has been understating top speeds by at least 10mph. I noticed this on the paper-run hill this summer, achieving only 35mph despite spinning out in top gear. A test run with the 705 and my iPhone confirmed what I thought - the 705 is recording everything right except top speed.
I checked if the recording method has changed - it was set to Smart Recording and I wondered if I had it set to Every Second before. However a look at my history shows that 200km rides are taking the same amount of data per file as they used to.
Any ideas?