Strange HR rates and Height

[frietsje]

Hi,

2 things.
One is that my HR belt gives strange values during the workout. I have 2 examples:
Example 1
Example 2

You can see that suddenly the heart rate is going down, way below the actual HR (you can see that my pace isn't slowing down)
I doubt that it has to do with not enough sweat for contact, because in both examples, it was around 30 degrees Celcius.... Is this just the end of my battery?

Second,
For fun, i had the watch running on my flight back from spain. Here you can see the log file:
Flight log

Quit strange that the height stops at 2178 meters. We were at +- 10 km, and besides, I think we went a lot faster to 2178 meters. Maybe this has to do with the air pressure or something in the plane?