sometimes, but not always, tell me I'm going twice as fast as I really am?

Seems to be high speed that upsets it. Then when I slow down it thinks I'm still going fast. I have to stop, and then ride again, and it's fine. (til next time)

Batteries need replacing in TX or RX? They are not that old (maybe a year).

My 725 was garbage at speed and cadence….. Batterys in sensors used to last 6 months or so before giving erratic readings ….

Mine was fine.

Power lines gave erratic readings sometimes due to interference, but this was rare.

Could be the speed sensor itself but I dunno how – it's actually got a reed relay in it that's activated by the magnet – hard to see how that'd click accidentally. Tried adjusting the position of the sensor relative to the magnet?

I'm happy with the kit – it does everything I need and I never usually have a problem. I'll try replacing the batteries in the sensors and make sure it's all clean.

hard to see how that'd click accidentally.

agree. I can imagine it missing a pass or two of the magnet, especially at speed, but seeing it when it's not there is weird!