why my cadence suddenly drop ?

In my non-expert opinion...if you double up that number you get your "usual" cadence right?! I don't know what causes it to record it that way... do you get the data from a HRM-run strap or only from the watch

looks like your watch is recording alternately the purple line and the red line, which probably means it is faulty

The same thing happens to mine. I think that this happens when I look at my watch during a run. Because I'm holding the watch still to read it, it thinks I am skipping steps, hence the cadence drops by half. Frustrating because it seems easy to fix. Does cadence work for others?

The same issue happed when I ran on a treadmill.

I mentioned this in the post https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-745/255598/ridiculous-cadence-when-running-on-treadmill

Is any feedback or improvement from Garmin?

Is anyone having the same annoying problem?

Hi, I tried to clear all my activities history on watch, then I reset the watch to factory setting.

Now it become normal. Cadence back to 185 to 200. No more red dot in between. It works for me.

Hope it work for u all too. 

Thanks 

Thanks for your reply. I will try it soon.