Exchange New 955 and still battery drain

Return it again, it is unacceptable 

Seems to be really intermittent, I ran 20 miles / 3 hours this morning. Backlight off, max accuracy GPS, external HRM, and used less than 15%. 

I’ve never really had battery drain issues to your level. 

that really stinks. it's alarming to hear about such battery drains and so many don't experience any drains at all. I can only guess there are some differences in setups including but not limited to: phone type and GC app connection, BT/ANT sensors, watch face, status of GC app (still left on a particular screen) and other things.

I thankfully have been in the latter camp but really empathize with folks that have had issues.

for me, everything behaves as expected and my "bad scenarios" are when it inexplicably drops about 3-5% in a couple of hours but it then "rights itself." I used to reset my watch when I saw that happening, but the last few times, I have let it go and confirmed that it does ultimately settle out.\

for your particular case here, somehow things are still running after the activity is saved. are you using any external sensors?

<sarcams>I'm very surprised that the battery drain isn't a hardware issue that can be fixed by replacing the watch. Who would have guessed that?

Maybe the new watch is having same hardware issue and it also needs to be replaced!</sarcams>

But sorry to hear, I have no solution to give to you, mine battery usage is ok, so it's something something in your use case, but what could that be is hard to say. Maybe trying to run without any external sensors and phone paired/connected that does it still happen.