Back-lap button doesn't stop anymore GPS on Ultra-Run mode ?

Never did that for me, it ran the rest timer but distance was still accumulating. I tested that carefully on the first beta release to find out how it behaved. 

It's not a function I've ever used, but according to Garmin the lap key has four different functions in Ultra Run and you have to select the mode you require.....

support.garmin.com/.../

True, but none of those stop distance accumulating. It's just toggling on/off the rest timer and the standard lap key behaviour. 

But, at the beginning, when the ultra-run mode has been released, I've done some tests and pressing back-lap button change screen AND stop GPS because pace and speed was at 0 during the rest time and distance was not growing although I move to simulate a rest during a race.

After another press as I was leaving rest, pace and speed move.

Now, the same test shows me that pace and speed are not to 0 and distance continue growing.

No offence, but are you confident that you moved far enough for the distance to increase? Because I did exactly the same test on 15.01, where it was released, and it increased. I was disappointed, but could see a positive side that it will keep increasing if I forgot to push lap again leaving the aid station. 

Puzzling. I have a 6x. What's your device? Was that on the beta, or on the first full release with ultra run?

it stops GPS (since you're supposed to be out of GPS reach in sleep/eat areas) but keeps registering distance from the accelerometer.

drkglb said:

it stops GPS (since you're supposed to be out of GPS reach in sleep/eat areas) but keeps registering distance from the accelerometer

No. 

This is from my test with 15.01; the dark blue loop was where I had the watch in rest, and was walking around slowly to see if distance was accumulating. It's clearly a GPS track to follow the loop like that. (Not many points because Connect doesn't plot every recorded point). 

@drkglb : yes ! it's exactly what it was supposed to do.

...

Thanks Chris. 

I'm confident my unit at least has never worked as the OP described, but I think that would be an improvement of it didn't accumulate distance during rests.