From 235 to 245M: why are calories way off?

Hi all,

Moved  from 235 to 245M: why are calories way off?

235 gave me circa 2400 kcal per day for 10,000 steps per day 

I'm 150lbs male and that;s always been spot on for me.

No changes to user stats or HR zones on 245. 
10k steps now gives me 1800 - 2000 if lucky. 

It also gives me far less for active calories for comparable activites.

Has an algorithim changed? Software bug?