All + Multi-band - incorrect recording

I looks like what happens if you go inside something with no GPS Signal. The other one got lucky or just paused.

Also a phone is bigger, has a bigger antenna and can probably lock on a bad signal longer.

That's called "GPS drift". Please read this text:
What Can Cause GPS Accuracy Issues on My Fitness Device?
especially the part "Stopping Without Pausing During an Activity"

No, other one didnt pause. (but i verified and garmin added 1,5km to distance when we were inside building...)
But its no point to make pause... i want to record how long i was rested so its pointless to make a pause.

its weird that it also occur with multi-band
so i think there should be an option to pause recording track without pausing duration of training

You can always open an IQ widget to stop GPS but keep the activity running. But you have to do it twice as it will stop at the second time currently.

Sorry couldn't resist, but this bug is kind of the solution here. 

Other issue was while snowboarding, almost all rides was accurate but 3 of them (green arrows) looks like it stops recording for around 1 minute and catch signal back at the bottom of ski slope and miss the half of each 3 rides

Hi!

I see you have  "data recording "Every second"

I have watched a review comparing "Every second" and "Smart" modes. And in "Every second" mode they had a similar "GPS Drift" issues. But with Smart mode thay did not have this issue at the same place.

Try "Smart mode" it also takes into account your heart rate, speed, elevation.. if I understand, in Smart mode the watch can guess, if you are not moving even in case of "GPS drift". 

Smart Recording vs. Every Second Recording on Garmin Devices

It's going to be due to a combination of factors, such as the shelter obscuring the view of the satellites, multi-path errors due to the GPS signal bouncing off the mountains and possibly the shelter, and the fact that the satellites in the constellation move around and don't always provide sufficient coverage for an accurate location fix.

Ok I can understand that. So solution is to pause activity, but in that case we are missing option to pause recording position without pausing activity duration