UPDATE: I think i probably know what could be causing the lag, As i went near to a big plot of water the lag started and when i moved away from the water it stopped. The game doesn't lag anywhere else in the world and i'm just wondering why release updates when it doesn't fix the problem.
I managed to get a little video of evidence of lag on 1.2.3.6, I uploaded it to my twitter and i don't know if a link to the video would be allowed on here.
It's happening to me too, It doesn't lag when inside your base for example but if you try going outside it really lags. Isn't there any way to make this issue a top priority to be seen and fixed straightaway because personally i don't think the problems are taken any notice of.Also no has reported on other sites such as reddit or on twitter and i've seen people playing on twitch with no problems whatsoever so i don't know if it is console only experiencing this problem.
As of todays update this issue appears to be solved. Thanks guys!
Also happening on my Lumia 950, as well as for users on Reddit and Windows Central. Crashes immediately and consistently when tapping 'Play'.
https://www.reddit.com/r/windowsphone/comments/3tpbpo/minecraft_pocket_on_lumia_950/
UPDATE 2: On second thoughts it may be the water causing it but there is something at the back of my base causing lag but nowhere else am i having the trouble. Anybody got any ideas.