Red light on back swing

I'm experiencing exactly the same issue.

The update fixed the original problem of the unit going into standby/disconnecting after every swing without recording any data but has left me in this situation.

Light flashes green, start backswing and the light goes solid red. Nothing records, the unit goes back to flashing green and repeat.

I still haven't managed to track a single shot.

I’m sorry to hear that but glad I'm not the only one.

I have sent an email to support, I will let you know the response when they get back to me tomorrow.

Thank you. If you're happy to post their response then I'd appreciate that.

Same problem here. Got my R10 today. At first it would just go to standby mode all the time and not register anything. Updated the firmware and that helped. Was able to hit a few shots using the range feature of the garmin golf app. Then I switched to E6 and the only way I can hit any shots is to take my backswing, wait for 5 seconds for it to turn green, then hit my shot... 

Whenever i move my club towards the R10 the light turns red and the swing isn't registered.

Not impressed by this expensive unit I must say

Same here, happened for the first time after updating to 3.90. I turned the unit off and reconnected again and it was fine. Had mine since August and no issues in this area since I've owned it. 3.80 was working really well and I was reluctant to update, but went ahead anyway. Hopefully it's just a minor glitch...

I connected my unit via usb to an old mac. Browsed the USB drive that appeared, and deleted the Garmin folder. After this garmin express wanted me to upgrade unit firmware (even i already had updated to 3.9). After this the unit works slightly better. it still flashes red in my backswing, but contrary to before it records my swing. Though the distance of my shots are way shorter than i'd expect. Like 30-40% shorter for all clubs I tested. 

I’ve just encountered the same issue. Did you get a resolution for this? 

The unit is supposed to go red once you start the swing, that means it is detecting your swing. If it is not displaying a shot, I would make sure the light is green, then swing, with trying hard not to "waggle". If it is still not picking up the shot, I would make sure you have enough space and there is not any interference like fans/blowers/heaters in front of the R10. 

Thanks Alex. Useful to know ready light means active. Have used the unit 3 times. First time picked up all shots, 2nd time picked up about 50% and yesterday picked up the first four shots and nothing after that. All at same range with same set up and no interference.