Insane Battery drain since 15.10

Hi,

Since updating my Fenix5 to 15.10 the Battery drains about 1% per hour.
Whats wrong?
With Firmware 12.40 it needed about 6% per DAY.
With newer updates since 12.40 it gets worse and worse, but now with 1% per hour …. thats insane.

What can I do?
Is there any possibilty to Downgrade?

With best Regards,
Patrick